THE 

GAS-ENGINE  HANDBOOK, 

A  MANUAL 

OF  USEFUL  INFORMATION 
FOR  THE 

DESIGNER   AND    ENGINEER. 

BY 

E.  W.  ROBERTS,  M.  E., 

Author  of  The  I.  C.  S.  Textbooks  on  Gas,  Gasoline  and 
Oil  Engines. 


FIRS  T  EDI  TION.       FI RS  T  THO  US  AND. 


CINCINNATI: 

THE  GAS  ENGINE  PUBLISHING  Co. 


GOODALL   BUILDING. 


NOTEX 

It  is  the  earnest  desire  of  the  publishers  and 
of  the  author,  that  this  work  shall  be  a  standard 
of  reference  for  those  interested  in  gas  enginery. 
They  will,  therefore,  be  pleased  to  have  their  atten- 
tion called  to  any  errors  of  commission  or  omission 
in  this  book. 

THE  PUBLISHERS. 


COPYRIGHT,  I9OO, 
BY 

THE  GAS  ENGINE  PUBLISHING  CO 


PREFACE. 


It  was  during  the  preparation  of  a  series 
of  textbooks  on  the  gas  engine  for  the 
International  Correspondence  Schools,  that 
the  author  was  most  forcibly  impressed 
with  the  dearth  of  matter  upon  American 
practice  in  this  motive  power.  It  is  a 
recognized  fact  that  designers  on  the  other 
side  of  the  Atlantic  do  not  follow  methods 
that  meet  writh  the  approval  of  engineers  in 
the  United  States,  yet  the  only  truly  valu- 
able works  on  gas-engine  design  that  have 
made  their  appearance  in  the  Bnglish  lan- 
guage are  by  English  authors.  Unhappily, 
the  average  gas-engine  manufacturer  in 
this  country,  guards  any  information  he 
may  possess  with  the  jealousy  that  is 
scarcely  to  be  explained  on  ordinary 
grounds.  While  there  are  a  number  of 
good  works  on  steam-engine  design,  the 
gas  engine  has  been  surprisingly  neglected. 
Although  the  author  does  not,  in  the  present 
work,  hope  to  cover  the  entire  subject  of 
gas-engine  design  he  has  endeavored  to 

435986157 


place  upon  its  pages  a  sufficient  number  of 
rules  and  formulas,  to  enable  any  intelli- 
gent draftsman  to  design  a  gas  engine 
without  difficulty.  Many  of  the  formulas 
are  new  and  have  not  appeared  in  any 
works  by  other  authors.  They  have  been 
derived  for  the  most  part  from  tables  of 
dimensions  of  some  of  the  most  successful 
American-built  engines,  and  have  been 
used  by  the  author  in  making  up  his  own 
designs. 

It  has  been  the  endeavor,  to  place  within 
the  smallest  possible  compass  a  number  of 
useful  rules  and  hints,  that  may  be  of  value 
not  only  to  the  designer,  but  also  to  the 
engineer  who  has  the  care  of  a  gas  engine. 
The  chapter  on  testing  has  been  given 
more  attention  than  might  perhaps  have 
.  been  thought  necessary  in  a  book  of  this 
size,  but  it  also  covers  many  points  regard- 
ing the  calculation  of  horsepowers  and 
other  items  purposely  omitted  from  the 
other  portions  of  the  book.  This  portion 
of  the  work  was  founded  upon  the  methods 
employed  at  the  Cornell  University. 

The  author  has  drawn,  in  a  few  instances, 
from  other  works  upon  the  same  subject. 
In  preparing  the  matter  on  design,  he  has 
received  many  useful  hints  from  the  works 
of  Mr.  Frederick  Grover  and  Mr.  William 
Norris,  the  two  English  writers  already 


referred  to.  A  part  of  the  data  in  the  table 
of  heat  values  is  from  a  similar  table  in 
the  work  of  Mr.  Gardner  D.  Hiscox.  The 
mechanical  tables  are  from  various  pocket- 
books  and  from  the  works  already  referred 
to. 

Much  that  the  writer  would  have  desired 
to  include  in  the  present  work,  it  has  been 
necessary  to  omit  for  lack  of  space.  He 
has,  therefore,  given  only  such  matter  as  he 
has  judged  most  useful,  and  which  he  has 
found  most  frequently  the  subject  of  in- 
quiries in  the  question  and  answer  columns 
of  the  technical  papers. 

B.  W.  ROBERTS. 

Cincinnati,  March,  1900. 


CONTENTS. 


CHAPTER  I.  PAGE 

Introductory  :  The  principles  of  opera- 
tion of  the  cycles  at  present  in  use.  .  .  I 

CHAPTER  II. 

Comparison  of  the  Three  Cycles :  The 
advantages  and  disadvantages  of  each.  13 

CHAPTER  III. 

Gas-Kngine  Fuels  :  The  principal  fuels 
in  use,  with  a  table  of  heat  values. ...  17 

CHAPTER  IV. 

Starting  and  Stopping:  The  order  of 
procedure  in  each  case 22 

CHAPTER  V. 

Care  of  an  Kngine  :  How  to  keep  a  gas 
engine  in  good  running  order 27 

CHAPTER  VI. 

Gas-Engine  Troubles:  Where  to  look 
for  the  cause  of  trouble,  and  the  rem- 
edies which  apply 35 


CHAPTKK   VII.                     TMGE 
Gasoline  Engines  :  How  they  differ  from 
a  gas  engine.     Special  attachments  re- 
quired for  the  use  of  gasoline 41 

CHAPTER  VIII. 

Handling  a  Gasoline  Engine :  Special 
rules  for  the  care  of  a  gasoline  engine  49 

CHAPTER  IX. 

Igniters:  Classification  of  the  various 
devices  and  examples  of  the  principal 
types 54 

CHAPTER  X. 

Valve  Mechanisms  :  An  explanation  of 
the  various  systems  in  general  use.  ...  73 

CHAPTER  XI. 

Governors  :  A  classification  of  the  gov- 
ernor methods.  The  limitations  of 
each  method.  Examples  of  the  prin- 
cipal mechanisms 87 

CHAPTER  XII. 

Starters  :  Devices  for  starting  large  en- 
gines and  how  they  are  used 97 

CHAPTER  XIII. 

Engines  for  Automobiles :  The  chief 
requisites  for  engines  of  this  class. 
The  speeds  at  which  they  should  run. 
How  to  avoid  vibration.  Regulation .  103 


CHAPTER  XIV.                   PAGE 
Gas-Engiiie  Diagrams  :     How  to  lay  out 
an  ideal  diagram.     How  to  read  a  di- 
agram.     Bxamples   of  good  and  bad 
diagrams 108 

CHAPTER  XV. 

Gas-Engine  Dimensions  :  How  to  com- 
pute the  cylinder  diameter  and  the 
stroke  of  a  gas  engine  of  any  size. 
How  to  find  the  speed  at  which  the 
engine  should  run 121 

CHAPTER  XVI. 

The  Cylinder :  Rules  and  formulas  for 
the  design  of  a  gas-engine  cylinder. . .  129 

CHAPTER  XVII. 

Valves  and  Valve-Boxes :  Examples  of 
valve  arrangement.  Proportions  of  the 
various  parts  of  a  gas-engine  valve. 
Formulas  for  valve- box  design 136 

CHAPTER  XVIII. 

The  Piston,  the  Connecting-Rod  and  the 
Crankshaft :  Examples  of  each,  and 
formulas  for  the  proportioning  of  the 
various  parts 146 

CHAPTER  XIX. 

The  Engine  Frame :  An  example  of  a 
frame  for  a  horizontal  engine.. 157 


CHAPTKR  XX.                     PAGE 
Flywheels  :    How  to  compute  the  weight 
of  a  flywheel   for  any  gas  engine  and 
for  any  service 160 

CHAPTER  XXI. 

Balance-weights  :  Computations  of  the 
weight  of  a  gas-engine  counterbalance. 
Two  methods  that  are  in  use 167 

CHAPTER  XXII. 

Foundations  :  Materials  of  which  a  foun- 
dation should  be  built.  Formula  for 
computing  the  weight  of  an  engine 
foundation 171 

CHAPTER  XXIII. 

Miscellaneous  Formulas  :  Formulas  for 
the  diameter  of  the  camshaft,  the  vol- 
ume of  the  muffler,  the  horsepower  of 
a  marine  engine,  the  diameter  of  a 
screw  propeller 177 

CHAPTER  XXIV. 

Testing:  A  full  description  of  all  nec- 
essary operations  for  a  gas-engine  test 
for  any  purpose,  with  rules  for  work- 
ing up  the  data  obtained 180 

CHAPTER  XXV. 

Selection  :  General  rules  for  the  selec- 
tion of  a  gas  engine 203 


TABLES.  PAG* 

Heat  values  of  various  gases. 
Capacity  of  cylindrical  vessels. 
Dimensions  of  gas  and  water  pipe.  .        .  208 
Areas  and  circumferences  of  circles.  .  .  .209 
Index 2I5 


CHAPTER  I. 

INTRODUCTORY. 

The  Gas  Engine,  properly  so  called,  is  a 
type  of  the  internal-combustion  engine. 
Its  first  conception  seems  to  have  been  by 
one  Abbe  Hautefueille,  who  proposed  a  mo- 
tor driven  by  a  gunpowder  as  early  as  1678. 
From  that  time  until  1862  many  proposi- 
tions were  made  and  some  partially  success- 
ful engines  were  built  by  various  experi- 
menters. In  the  latter  year,  there  were 
already  in  existence  the  gas  engines  of 
Ivenoir  and  Hugon,  but  very  wasteful  of  fuel. 
In  1862  M.  Beau  de  Rochas,  a  French  en- 
gineer, made  the  following  propositions, 
which  he  embodied  in  a  patent  of  that  date. 
They  were  as  follows: 

I.  The  largest  cylinder  capacity  with  the 
smallest  circumferential  surface. 

II.  Maximum  speed  of  piston. 

III.  Greatest  possible  expansion. 

IV.  Highest  pressure  at  the  beginning  of 
the  stroke. 


These,  he  averred,  should  be  the  aim  of 
'every  gas-engine  designer  to  carry  out  in 
his  engine.  With  the  exception  of  propo- 
sition II,  every  engine,  since  the  successful 
.advent  of  the  Otto  engine,  has  been  de- 
signed with  these  principles  in  view.  Ow- 
ing to  certain  practical  limitations,  high 
piston  speeds  have  not  been  found  advisa- 
ble. 

It  was  M.  Beau  de  Rochas  who  first  pat- 
ented what  is  popularly  known  as  the 
"  Otto  Cycle."  This  cycle  requires  four 
strokes  of  the  piston  for  its  completion. 
The  first  stroke  draws  in  the  charge  of  gas 
-and  air,  the  second  stroke  compresses  the 
charge,  on  the  third  stroke  ignition  takes 
place  at  the  dead  point,  followed  by  explo- 
sion of  the  gaseous  mixture  and  the  expan- 
sion of  the  products  of  combustion,  and  on 
the  fourth  stroke  the  burnt  gases  are  ex- 
pelled from  the  cylinder.  This  series  of 
operations  is  that  employed  by  nearly  all 
gas  engines  in  use  at  the  present  time. 

This  cycle  was  not  put  into  a  practical  use 
in  a  working  engine  until,  in  the  year  1876 
Dr.  Abel  Otto  brought  out  the  first  "  Otto 
Cycle  "  engine,  producing  a  motor  which  so 
far  surpassed  in  economy  all  engines  that 
superseded  it  as  to  drive  its  competitors 
from  the  field.  This  cycle  of  operation  has, 
because  of  its  being  first  put  into  practical 


shape  by  Dr.  Otto,  been  improperly  termed 
the  "  Otto  Cycle,"  although  the  credit  of  its 
first  inception  belongs,  without  question,  to 
M.  Beau  de  Rochas.  It  is  also  known  as  a 
four-cycle  engine,  although  this  term,  to  be 
strictly  correct,  should  be  four-part  cycle, 
because  it  consists  of  the  four  distinct  oper- 
ations just  described.  Modern  writers  have 
been  placing  the  credit  where  it  belongs,  and 
this  series  of  operations  is  now  generally 
termed  the  Beau  de  Rochas  cycle.  The  au- 
thor, however,  prefers  the  same  descriptive 
term,  "  four-cycle,"  and  as  such  it  will  be  re- 
ferred to  throughout  this  work. 

The  practical  operation  of  the  four-cycle 
engine  can  be  most  clearly  understood  by 
reference  to  Fig.  I,  in  which  a  diagramatic 
form  of  the  engine  is  shown  with  the  indi- 
cator diagram  given  by  the  engine  placed 
directly  above  the  cylinder.  Since  it  re- 
quires two  revolutions  of  the  crankshaft  K 
to  complete  the  cycle,  the  principal  points 
of  the  cycle  are  shown  on  the  two  circles 
drawn  about  the  crankshaft  as  a  center. 
Similar  points  upon  the  diagram,  the  piston 
travel  and  the  rotation  of  the  crankpin  P, 
are  indicated  by  the  same  letters.  The  let- 
ters indicating  points  on  the  piston  travel 
are  primed,  and  those  indicating  similar 
points  on  the  crank  circle  have  a  double 
prime.  Thus,  the  point  of  ignition  is  indi- 


cated  on  the  diagram  by  Bx  on  the  line  of 
piston  travel,  and  by  Bx/  on  the  crank  circle. 
Taking  the  series  of  operations  in  their 
regular  order,  they  are  as  follows  : 

Suction  of  air  from  a  to  A  on  the  outward 
stroke,  compression  from  A  to  C  on  the  in- 
ward stroke,  ignition  taking  place  at  B,  just 
before  the  end  of  the  stroke  is  reached, 
thus  giving  a  "  lead  "  to  the  ignition  which 
should  just  be  sufficient  to  bring  the  point 
of  maximum  pressure  D,  at  the  beginning 
of  the  next  outward  stroke  ;  this  lead  being 
necessary  because  of  a  lag  in  the  process  of 
ignition,  which  takes  the  time  required  by 
the  piston  going  from  B  to  C  to  fully  in- 
flame the  charge  of  gas  and  air.  From  D 
to  F  the  piston  is  passing  011  a  second  out- 
ward stroke,  the  exhaust-valve  X  opening  at 
K,  just  in  time  to  allow  the  expansion  line  D 
F  to  reach  atmospheric  pressure  at  the  end 
of  the  second  outward,  or  expansion,  stroke. 
The  return  stroke  takes  place  from  F  to  a, 
the  piston  making  a  second  return  stroke, 
driving  the  products  of  combustion  through 
the  exhaust-pipe  by  way  of  the  valve  X,  . 
completing  the  cycle. 

A  modification  of  the  four-cycle  engine 
was  brought  out  by  its  inventor,  Mr.  Du- 
gald  Clerk,  in  the  year  1880.  In  this  engine, 
using  an  auxiliary  pump,  a  power  stroke 
was  obtained  for  each  revolution  of  the 


crankshaft.  The  charge  was  admitted  to 
the  engine  cylinder  under  pressure  and  just 
at  the  end  of  the  expansion  stroke,  driving 
the  exhaust  gases  out  through  ports  in  the 
sides  of  the  cylinder,  which  were  uncovered 
by  the  piston  just  at  the  end  of  the  stroke. 
This  arrangement  eliminated  both  the  suc- 
tion and  the  exhaust  strokes  required  in 
the  regular  Beaii  de  Rochas  cycle.  Clerk's 
engine  was  the  pioneer  of  what  is  now 
known  as  the  two-cycle  type  ;  that  is,  an  en- 
gine which  completes  its  cycle  in  two  revo- 
lutions of  the  crankshaft. 

Following  the  introduction  of  the  Clerk 
engine  came  a  class  of  engines  which,  in- 
stead of  having  an  auxiliary  cylinder  to 
compress  the  charge,  used  for  that  purpose 
an  enclosed  crank-chamber.  The  inward 
stroke  of  the  piston  draws  into  the  crank- 
chamber  the  charge  of  gas  and  air  through 
a  check-valve,  and  on  the  outward  stroke 
the  charge  is  compressed.  Just  before  the 
piston  reaches  the  end  of  its  stroke  its  end 
passes  an  exhaust-port  in  the  side  of  the 
cylinder,  and  in  some  engines  a  port  lead- 
ing to  the  crank-chamber  is  passed  imme- 
diately afterward. 

In  another  type,  communication  was  made 
by  means  of  a  poppet  valve.  The  pioneers 
of  this  type  were  the  Nash  and  the  Day 
engines.  The  former  used  a  mechanically 


opened  poppet  valve,  and  the  latter  an  ad- 
mission port  in  the  cylinder  wall.  Quite  a 
number  of  engines  of  the  Day  type  are  in 
successful  operation  at  the  present  time. 

The  principle  of  the  operation  of  the  Day 
type  of  the  two-cycle  engine  is  shown  in 
Fig.  2,  in  a  similar  manner  to  that  of  the 
four-cycle  engine  shown  in  Fig.  I ;  the  same 
method  of  notation  as  regards  letters  being 
used  in  this  figure,  the  only  difference  be- 
ing that  where  the  two  crank  circles  are 
used,  the  inner  one  indicates  the  series  of 
operations  taking  place  in  the  crank-cham- 
ber, and  the  outer  indicates  the  series  of 
operations  taking  place  in  the  cylinder. 
The  piston  makes  an  inward  stroke  from  b 
to  a,  causing  a  partial  vacuum  in  the  crank- 
chamber  and  drawing  the  explosive  mix- 
ture through  the  valve  P.  On  the  following 
outward  stroke  the  mixture  in  the  crank- 
chamber  is  compressed  to  a  pressure  of 
about  five  pounds  to  the  square  inch.  As 
the  piston  uncovers  the  inlet  port  S,  the 
pressure  within  the  crank-chamber  drives  a 
portion  of  its  contents  into  the  cylinder  C, 
and  on  the  next  inward  stroke  of  the  piston 
this  charge  is  compressed,  as  shown  on  the 
diagram  from  A  to  C,  ignition  taking  place  as 
in  the  four-cycle  at  B,  pressure  rising  to  D, 
the  piston  making  outward  stroke,  exhaust- 
ing  at  E,  and  the  gases  reaching  atmospheric 


pressure  again  at  A,  the  exhaust-port  being 
opened  by  being. uncovered  by  the  piston. 
In  the  meantime  a  charge  is  being  drawn 
into  the  crank-chamber  as  before,  has  been 
compressed,  and  the  inlet-port  S  being  un- 
covered immediately  after,  the  contents  of 
the  crank-chamber  rushing  through  S  is 
deflected  by  means  of  the  plate  R  on  the 
piston  to  the  top  of  the  cylinder,  effectu- 
ally driving  the  products  of  combustion 
through  the  port  M.  Returning  to  the  se- 
ries of  operations  in  the  crank-chamber, 
the  port  S  opens  just  as  the  piston  reaches 
the  point  E,  the  pressure  immediately  drop- 
ping and  reaching  the  pressure  of  the  at- 
mosphere at  about  the  time  port  S  is  closed 
by  the  return  of  the  piston.  It  is  unneces- 
sary to  repeat  the  explanation  of  the  points 
on  the  diagram  taken  from  the  cylinder  C, 
as  they  are  in  all  respects  similar  to  the 
four-cycle  engine  illustrated  in  the  Fig.  i. 

The  Clerk  engine  is  no  longer  built. 
Nearly  all  two-cycle  engines  being  manufac- 
tured at  the  present  time  are  built  after  the 
Day  pattern.  In  the  latter  part  of  1897,  a 
new  cycle  was  brought  to  the  attention  of 
the  public.  This  cycle  comprises  the  se- 
ries of  operations  which  were  the  inven- 
tion of  Herr  Rudolph  Diesel,  a  German 
scientist.  The  Diesel  cycle  is,  like  the 
invention  of  Beau  de  Rochasr  a  four-part 


cycle,  requiring  two  entire  revolutions  of  the 
crankshaft  to  complete  the  series  of  opera- 
tions. The  first,  or  outward,  stroke  draws 
into  the  cylinder  a  charge  of  pure  air.  On 
the  following  return  stroke  the  charge  is 
compressed  into  a  space  at  the  end  of  the 
cylinder,  equal  to  about  7  percent  of  the 
entire  cylinder  capacity,  the  pressure  at  the 
end  of  the  stroke  being  approximately  550 
pounds  per  square  inch.  This  high  com- 
pression produces  a  temperature  of  the  air 
equal  to  that  produced  by  the  combustion 
of  the  fuel,  and,  in  consequence,  fuel  ad- 
mitted at  the  end  of  this  stroke  is  sure  to 
be  ignited  as  it  enters  the  cylinder.  The 
fuel,  whether  it  be  gas,  oil  or  other  com- 
bustible material,  is  forced  into  the  cylin- 
der at  a  pressure  higher  than  that  produced 
by  compression,  and  just  as  the  piston  is 
about  to  start  on  its  outward  stroke.  The 
fuel,  burning  as  it  enters,  keeps  the  temper- 
ature of  the  cylinder  contents  up  to  that 
produced  by  compression.  After  the  pis- 
ton has  reached  a  point  of  the  stroke 
representing  10  percent  of  the  whole,  the 
fuel  is  cut  off  and  the  products  of  combus- 
tion expand.  The  ensuing  return  stroke 
drives  the  exhaust  gases  from  the  cylinder. 
It  is  readily  seen  that,  owing  to  the  small 
compression  space,  the  exhaustion  is  very 
much  nearer  being  complete  than  in  those 


engines  using  the  cycle  of  Beau  de  Rochas, 
and  that  but  a  very  small  quantity  of  the 
products  of  combustion  remain  to  mix  with 
the  fresh  charge  This  series  of  operations 
may  be  better  understood  by  reference  to 
the  Fig.  3. 

The  same  manner  of  representation  is 
employed  as  in  Fig.  i.  Suction  of  a  charge 
of  pure  air  takes  places  from  a  to  A  on  the 
outward  stroke,  the  following  inward  stroke 
compressing  this  charge  until  the  point  B 
is  reached,  when  the  fuel  is  admitted  while 
the  piston  is  passing  from  B  to  C  and  is  cut 
off.  The  temperature  of  the  gases  is  con- 
stant during  admission  of  the  fuel,  the  line 
from  B  to  C  being  one  of  equal  tempera- 
ture known  as  an  isothermal.  From  C  to  E, 
expansion  proceeds  in  a  manner  similar  to 
that  in  the  original  four-cycle  engine,  the 
exhaust-valve  opening  at  D  and  the  pres- 
sure inside  the  cylinder  falling  to  atmos- 
pheric at  B.  The  range  of  temperature 
from  C  to  D  is  much  greater  than  that  from 
D  to  F,  in  Fig.  I,  and  represents  a  much 
higher  heat  efficiency  than  that  shown  on 
the  diagram  of  the  four-cycle  engine. 


CHAPTER  II. 

COMPARISON   OF  THE   THREE    CYCLES. 

The  four-cycle  engine  is  that  most  gener- 
ally manufactured,  and  it  has  the  advantage 
over  the  two-cycle  of  being  more  readily 
controlled.  With  a  properly  designed  four- 
cycle engine,  the  behavior  of  the  gases 
within  the  cylinder  is  known  beforehand. 
The  idle  stroke  gives  the  cylinder  a  chance  to 
cool  by  radiation,  no  pumps  nor  enclosed 
crank-chambers  are  necessary,  and  any  waste 
of  fuel  may  be  easily  remedied.  On  the  other 
hand,  the  four-cycle  engine  must  be  built  in 
large  sizes  when  compared  to  the  power  de- 
manded of  them,  the  many  idle  strokes  ne- 
cessitate extremely  heavy  flywheels  and 
make  close  regulation  most  difficult  to  ob- 
tain. Furthermore,  the  operation  of  the 
valves  occurs  but  once  during  two  revolu- 
tions of  the  crankshaft  and  necessitates 
some  form  of  reducing  motion  between  the 
crankshaft  and  the  camshaft  which  operates 
the  valves. 

The   two-cycle  engine  is,  as  a  rule,  more 


wasteful  of  fuel  than  the  four-cycle  engine, 
and  such  wastes  are  more  difficult  to  reme- 
dy in  this  type  In  many  of  these  engines 
much  trouble  is  experienced  with  prema- 
ture explosions,  usually  called  "  back- 
firing," and  in  the  Day  type  of  two-cycle 
engine  the  charge  quite  frequently  explodes 
in  the  crank-chamber.  The  bulk  of  these 
troubles  is  fortunately  confined  to  engines 
built  by  designers  who  have  an  imperfect 
knowledge  of  the  type,  and  who  fail  to  de- 
sign their  engines  with  the  proper  propor- 
tions. 

Time  should  always  be  given  the  exhaust 
gases  to  fall  below  the  pressure  of  the 
crank-chamber  before  the  inlet-port  to  the 
cylinder  is  uncovered.  It  is  also  important, 
when  running  a  two-cycle  engine,  to  re- 
member that  much  more  heat  is  being 
given  off  through  the  cylinder  walls  than  in 
a  four-cycle  engine  of  the  same  power  dur- 
ing the  same  period,  hence  the  supply  of 
jacket  water  must  be  greater  in  consequence. 

A  two-cycle  engine  will  shut  down  more 
quickly  from  lack  of  water  than  will  a  four- 
cycle. Also,  because  of  the  rapid  succession 
of  explosions  in  the  cylinder  of  a  two-cycle 
engine,  greater  pains  should  be  taken  to 
avoid  projections  into  the  cylinder  which 
are  not  so  placed  that  they  may  be  kept  at 
a  comparatively  low  temperature. 

M 


These  engines  are  being  better  under- 
stood as  the  makers  gather  knowledge  from 
experience,  and  the  above  objections  have, 
in  several  cases,  been  entirely  overcome. 
So  many  and  manifest  are  the  advantages 
of  more  frequent  impulses  and  less  weight, 
both  in  the  engine  itself  and  in  the  fly- 
wheels, that  the  adoption  of  the  two-cycle 
type  is  being  seriously  considered  by  a 
number  of  manufacturers.  In  fact,  the  two- 
cycle  engine,  for  large  power-units  where 
the  fuel  employed  is  blast-furnace  gas,  has 
been  in  use  for  some  time  and  found  to  give 
satisfaction.  Instead  of  having  an  enclosed 
crank-chamber,  these  engines  are  supplied 
with  a  pump  which  first  drives  a  volume  of 
pure  air  through  the  cylinder,  clearing  it 
entirely  of  the  products  of  combustion  re- 
maining from  the  previous  charge.  The 
fresh  mixture  follows  the  charge  of  pure 
air,  and  none  of  the  fuel  is  wasted,  while  the 
clean  cylinder  increases  both  the  efficiency 
and  the  capacity  of  the  engine. 

The  Diesel  motor  is  not  at  present  upon 
the  market  in  sufficient  numbers,  nor  for  a 
length  of  time,  that  would  make  it  feasible 
to  draw  conclusions  of  any  kind  with  regard 
to  the  future  of  the  engine.  The  engine  is 
a  grand  conception  theoretically,  and  the 
heat  efficiency  is  much  higher  than  that  of 
any  heat  engine  in  use.  The  scheme  of 


regulation  is  similar  to  that  which  has 
proven  so  successful  in  high-speed  steam 
engines,  and  it  has  been  shown  by  actual 
tests  that,  in  practice,  the  engine  surpasses 
any  other  in  economy  of  fuel,  and,  besides, 
it  is  capable  of  being  run  with  such  inex- 
pensive fuels  as  the  low-grade  petroleums 
classed  as  fuel  oils  and  selling  in  quantities 
for  from  two  to  three  cents  per  gallon.  The 
question  therefore  remains:  will  the  great 
economy  of  the  motor  jtistify  the  added  ex- 
pense for  first  cost  of  the  engine?  Again, 
there  is  the  question  of  repairs  and  the 
durability  of  the  engine  under  the  high 
pressures  which  it  is  necessary  to  sustain  in 
the  cylinder.  All  this  remains  co  be  seen. 


16 


CHAPTER  III. 

GAS-ENGINE    FUELS. 

For  driving  a  gas  engine,  the  fuels  avail- 
able are  all  of  those  which  are  in  use  for 
other  purposes.  Many  of  these  fuels  need 
to  be  transformed  into  gas  before  they  are 
available  for  the  gas  engine,  but  many  of 
the  liquid  and  all  of  the  gaseous  fuels  may 
be  employed  directly  in  the  cylinder  with- 
out the  necessity  of  an  intermediate  proc- 
ess. There  is  no  fuel  not  in  a  gaseous 
state  already  that  may  not  be  transformed 
into  gas  by  one  of  the  many  processes 
known  to  science.  The  garbage  gathered 
from  the  streets  of  our  large  cities,  the 
waste  fat  from  the  slaughter-house,  the  fat 
abstracted  from  wool,  as  well  as  all  of  the 
animal,  vegetable  and  mineral  oils,  have 
been  at  one  time  or  another  transformed 
into  gas  which  could  be  used  to  drive  a  gas 
engine. 

The  amount  of  power  derived  from  a  cer- 
tain quantity  of  fuel  is  always  greater  by  3 


large  amount  when  the  fuel  is  first  made 
into  gas  and  then  used  to  drive  a  gas  en- 
gine, than  when  the  fuel  is  consumed  in  the 
firebox  of  a  steam  boiler  and  the  power  de- 
rived from  a  steam  engine.  Bven  with  coal 
as  a  fuel,  if  the  coal  be  made  into  gas  and 
the  gas  used  in  a  gas  engine,  it  is  found 
that  where  the  very  best  steam  engines 
give  but  a  horsepower  for  one  hour  on  i*^ 
Ibs.  of  coal,  the  same  amount  of  fuel  has 
^iven  1.8  horsepower  for  one  hour. 

The  gas-producer  which  is  required  for 
the  use  of  coal  in  connection  with  the  gas 
engine,  is  a  much  simpler  device  than  the 
steam  boiler,  and  requires  less  attention 
than  the  latter.  There  is  very  little  danger 
of  explosion  with  a  gas-producer  and  gas- 
engine  power  plant,  and  there  is  usually  a 
supply  of  gas  on  hand  in  the  gas-reservoir 
sufficient  to  permit  the  engines  to  be  started 
at  a  moment's  notice  without  the  necessity 
of  waiting,  as  when  getting  up  steam  for  a 
steam  engine. 

Fuels  which  are  most  difficult  to  burn 
under  a  boiler,  may  be  turned  into  gas  in  a 
gas-producer.  Even  gases  which  are  diffi- 
cult to  ignite  may  be  used  in  a  gas  engine. 
For  instance,  the  gas  produced  during  the 
process  of  extracting  iron  from  ore  in  the 
blast  furnace  is  at  times  so  poor  in  quality 
that  it  may  not  be  used  under  a  boiler,  while 

18 


when  compressed  in  a  gas-engine  cylinder 
it  is  found  to  ignite  readily. 

The  value  of  fuel  for  use  in  a  gas  engine, 
is  determined  in  a  great  measure  by  the 
number  of  heat  units  produced  when  a 
quantity  of  the  fuel  is  burned.  There  are, 
however,  several  other  considerations,  such 
as  the  pressure  derived  from  the  fuel  and 
the  percent  that  may  be  burned  in  the  gas- 
engine  cylinder.  In  the  process  of  making 
gas  from  fuels  a  percentage  of  the  heat  is 
employed  in  liberating  the  gas,  and  this,  of 
course,  can  not  be  given  account  of  in  the 
gas  engine. 

The  heat  values  of  the  various  fuels  are 
given  in  Table  i.  It  will  be  seen  that  the 
highest  heat  value  is  found  in  natural  gas. 
This  is  due  to  the  large  quantity  of  marsh 
gas  contained  in  natural  gas.  The  value  of 
natural  gas  as  a  fuel  varies,  even  when  the 
gas  is  taken  from  wells  very  close  to  one 
another.  It  may  be  said,  however,  that  the 
natural  gas  obtained  from  the  wells  in  west- 
ern Pennsylvania  exceeds  in  heat  value  that 
of  the  gas  in  the  Ohio  fields  from  Io%  to 


Gasoline,  in  spite  of  the  low  heat  value 
per  cubic  foot  of  vapor  shown  in  the  table, 
will  give,  for  the  same  size  engine,  a  power 
equal  to  that  derived  from  the  best  natural 
gas,  and  the  usual  custom  is  to  credit  gaso- 


line  with  giving  10%  more  power  than  an 
average  quality  of  natural  gas.  It  is  not 
possible  to  compute  the  horsepower  to  be 
derived  from  a  certain  engine  by  compari- 
son of  the  fuel  values,  since  the  gases  of 
low  heat  value  require  a  smaller  quantity  of 
air  for  their  complete  combustion,  and 
hence  a  larger  quantity  of  gas  may  be  taken 
into  the  cylinder  of  the  engine  at  each 
.stroke. 


HEAT   VALUES   OF    FUELS. 


FUEL. 

B.  T.  U. 

per  Ib. 

B.  T.  U. 

per  cu.  ft. 

Hydrogen  (n  32°  F.  .    .    . 

Carbon      .            ... 

62,030 
14  500 

343 

Carbon  monoxide  (CO). 
Penn.  heavy  crude  oil.  .    . 
Caucasian  heavy  crude  oil, 
Caucasian  light  crude  oil, 
Petroleum  refuse   .    .    . 
\nthracite  gas     

4,396 
20,736 
20,138 
22,027 
19,832 

2  2A.8 

539 

Bituminous  2fas 

1  d8/l 

28-candlepower  ilium,  gas, 
19-             «                 «         « 

J5- 

New  York  city  water-gas*, 
London  coal  gas.       .    .    . 

1  8  448 

950 
800 
620 
710.5  Ave 
668 

Gasoline  and  its  vapor  .    . 
Ethylene  C2  H4  
Marsh  gas  (Methane)  C  H4 
Nat.  gas,  Leechburg,  Pa., 
Nat  gas,  Pittsburg,  Pa  .    . 

11,000 
21,430 
23,594 

690 
i,677 
1,051 
1,051 
802 

Acetylene  C2  H2  

21,492 

868 
iSs 

I  ^O 

NOTE. — The  values  shown  in  the  above 
table  are  given  on  what  is  deemed  good 
authority,  but  they  will  not  be  found  to 
agree  with  all  similar  tables. 


*  Carbureted  gas  at  60    F.  and  at  30"  water  pressure. 
21 


CHAPTER  IV. 

/! 

STARTING    AND    STOPPING. 

Starting  a  gas  engine  is  a  simple  oper- 
ation if  a  few  easily-remembered  rules  are 
borne  in  mind.  These  rules  are  briefly  as 
follows : 

A  gas  engine  will  not  start  itself,  like  a 
steam  engine,  and  must  receive  sufficient 
turning  power  from  an  outside  source  to 
enable  it  to  take  up  its  cycle  of  operations. 

The  mixture  of  fuel  and  air  must  not  be 
too  rich  in  fuel  nor  too  poor  in  fuel,  for  in 
either  case  an  explosive  impulse  can  not 
be  obtained.  More  frequently,  trouble  oc- 
curs from  the  mixture  being  too  rich  in 
fuel. 

On  large  engines  the  compression  should 
be  relieved  and  the  ignition  given  a  nega- 
tive lead,  especially  when  starting  by  hand. 

Never  attempt  to  start  a  gas  engine  when 
it  is  connected  to  a  load,  unless  it  has  a 
powerful  starter. 

The  ignition  apparatus  must  be  in  good 


working  order,  and  this  must  be  seen  to 
before  attempting  to  start  the  engine. 

To  start  a  gas  engine,  it  is  always  a  good 
idea  to  have  a  regular  order  of  procedure 
and  to  stick  to  this  order  so  as  to  avoid  the 
chance  of  confusion  and  of  omitting  some- 
thing. A  good  way  to  proceed  is  as  follows  : 

First,  oil  the  engine  thoroughly,  filling 
every  oil-cup,  no  matter  if  one  or  more  is 
already  nearly  full. 

See  that  the  ignition  appliance  is  in  good 
order.  If  it  is  a  tube  igniter,  bring  the  tube 
to  the  proper  temperature  (usually  a  cherry 
red)  and  see  that  the  burner  is  at  the  right 
height  to  keep  the  tube  at  the  required 
heat.  If  an  electric  igniter  is  used,  unfasten 
the  wire  from  the  insulated  electrode  and 
brush  it  on  some  part  of  the  engine  to  see 
that  it  gives  a  good  flash. 

If  there  is  a  sight  plug,  it  would  be  well 
to  try  the  igniter  while  observing  its  behav- 
ior through  the  hole,  or  it  can  be  tried  by 
first  pressing  the  points  together  by  means 
of  the  igniter  mechanism  and  seeing  if 
there  is  a  circuit  by  drawing  the  wire  al- 
ready removed  over  the  end  of  the  insulated 
electrode,  then  letting  go  of  the  mechanism 
and  determining  in  the  same  manner  as 
before  if  the  circuit  is  broken. 

If  these  conditions  are  fulfilled,  and  when 
the  engine  is  turned  over  it  is  found  to 

23 


close  the  circuit  on  the  igniter-points,  the 
igniter  is  in  working  order. 

The  igniter  should  be  examined  periodic- 
ally and  the  points  cleaned  of  any  accumu- 
lation of  soot  or  other  foreign  matter  which 
may  occur.  The  frequency  of  this  exami- 
nation depends  entirely  upon  the  fuel  used, 
and  to  some  extent  upon  the  class  of  cylin- 
der oil  employed. 

After  determining  that  the  igniter  is  in 
working  order,  such  oil-cups  as  can  not  be 
conveniently  reached  when  the  engine  is 
running  should  be  turned  on. 

Next  set  the  starting-cam  to  start,  or  open 
the  relief-cock,  as  the  case  may  be,  and  if 
the  engine  is  fitted  with  a  changeable  ig- 
niter, set  this  also  to  the  starting  position, 
or  so  that  it  will  fire  after  the  crank  has 
passed  the  center. 

If  the  engine  is  to  be  started  by  hand,  set 
the  gas-valve  open  to  about  one  third  the 
opening  used  when  running;  usually  at  a 
point  on  the  gas-valve  dial  marked  "  Start." 
Then  turn  the  engine  over  in  the  running 
direction  until  it  takes  up  the  cycle,  j.  e., 
until  an  explosion  is  obtained. 

Next  take  hold  of  the  gas-valve  handle 
immediately,  and  open  it  gradually  to  the 
running  position  as  the  engine  increases  in 
speed.  Don't  be  too  precipitate  about  open- 
ing the  gas-valve,  as  the  engine  may  get 

24 


too  rich  a  mixture  and,  failing  to  ignite, 
slow  down  and  stop.  If  it  shows  signs  of 
stopping,  close  the  valve  a  little  at  a  time 
until  it  starts  receiving  impulses  again. 
While  opening  the  gas-valve  with  one  hand, 
the  other  may  be  occupied  in  closing  the 
relief-cock,  or  in  throwing  the  starting- 
levers  to  the  running  position. 

When  the  engine  has  reached  its  full 
speed,  the  load  may  be  thrown  on,  and  then 
the  remaining  oil-cups  must  be  opened  and 
the  water  turned  on  to  the  water-jacket. 

After  the  engine  has  been  running  a 
short  time,  and  if  the  load  is  very  nearly  a 
constant  one,  the  water  should  be  turned 
on  or  off  until  the  exit  water  is  of  a  tem- 
perature that  can  just  be  borne  comfortably 
by  the  hand. 

If  the  engine  is  fitted  with  a  starter,  the 
gas-valve  should  not  be  turned  on  until  the 
engine  has  made  one  or  two  revolutions. 
The  methods  of  using  the  starter  vary  with 
the  several  types,  and  their  use  will  be 
explained  in  a  chapter  on  that  subject. 

To  simply  stop  a  gas  engine,  it  is  neces- 
sary to  do  no  more  than  turn  off  the  fuel. 
The  order  for  turning  off  the  oil-cups,  etc., 
should  be  about  the  reverse  of  starting. 

First  turn  off  the  gas,  and  if  it  is  desired 
to  save  time  in  stopping,  brake  the  flywheel 
with  a  plank.  Then  turn  off  the  jacket 


water  and  turn  off  the  gas  from  the  burner, 
or  throw  the  igniter-switch.  If  there  is  110 
switch,  disconnect  one  of  the  wires  and 
hang  the  end  of  it  up  so  that  a  short  circuit 
may  not  occur.  Turn  off  the  oil-cups  and 
drain  the  water-jacket.  This  latter  proce- 
dure is  not  absolutely  necessary  except  in 
cold  weather,  but  it  is  not  a  bad  way  to 
prevent  the  accumulation  of  sediment  in 
the  jacket,  and  it  takes  but  little  time.  The 
habit  of  draining  the  cylinder  may  save  the 
engine  at  some  time  when  you  "  didn't  know 
it  was  going  to  freeze." 


26 


CHAPTER  V. 

CARE    OF   AN    ENGINE. 

The  proper  care  of  a  gas  engine  should 
be  the  pride  of  every  engineer  who  runs 
one.  In  every  shop  or  factory  where  a  gas 
engine  is  in  use,  it  should  be  left  in  the  care 
of  one  man  and  that  man  should  be  respon- 
sible for  the  condition  of  the  engine  at  all 
times.  "  Everybody's  dog  is  nobody's  dog," 
and  so  it  is  with  an  engine  which  is  left  in 
the  care  of  any  man  who  happens  to  be 
about  at  the  time  it  needs  attention.  Above 
all  things  keep  the  engine  clean,  well  oiled 
and  with  a  plentiful  supply  of  water  in  the 
tank,  when  a  tank  is  used,  or  with  sufficient 
flow  of  water  when  connected  to  a  pressure 
system. 

If  the  engine  is  a  new  one  when  first  re- 
ceived, it  is  well  to  determine  the  exact 
point  of  the  stroke  where  the  ignition  takes 
place.  This  can  be  done  very  easily,  with 
an  electric  igniter,  by  turning  the  engine 
over  until  the  igniter  snaps  for  breaking 
the  circuit,  and  marking  the  piston  so  as  to 

27 


have  a  point  of  reference  for  future  settings 
of  the  igniter.  All  igniter  mechanisms 
wear  more  or  less,  and  the  mark  on  the  pis- 
ton will  avoid  the  necessity  of  taking  an  in- 
dicator diagram  to  set  the  igniter. 

If  the  piston  is  so  situated  as  to  make  it 
inconvenient  to  make  a  mark  upon  it,  the 
mark  may  be  placed  upon  the  flywheel.  To 
mark  the  flywheel  for  this  purpose,  proceed 
in  one  of  the  following  ways  :  Turn  the  en- 
gine over  slowly  until  the  igniter  just  snaps. 
If  the  engine  has  been  turned  too  far  it  will 
be  necessary  to  make  a  complete  revolution 
again  in  order  to  be  certain  that  all  lost 
motion  is  taken  up.  After  the  flywheel  is 
in  the  right  position,  drop  a  .plumb-line  past 
the  center  of  the  crankshaft  and  mark  on 
the  rim  of  the  flywheel  opposite  where  the 
line  passes  it,  or  level  up  a  straight-edge  so 
that  it  passes  the  center  of  the  crankshaft 
and  mark  the  flywheel  as  with  the  plumb- 
line.  It  will  be  more  convenient  even  than 
the  above  methods,  if  the  flywheel  passes 
close  to  some  part  of  the  engine-frame  or 
bed,  to  mark  both  the  wheel  and  some  point 
on  a  stationary  part  of  the  engine. 

A  good  grade  of  machine  oil  should  be 
used  on  the  engine  bearings,  but  in  the 
cylinder  there  should  always  be  used  an  oil 
that  is  made  expressly  for  this  purpose. 
Never  use  the  heavy  cylinder  oils  that  are 

28 


sold  for  steam-engine  cylinders,  or  you  will 
soon  find  that  the  passages  are  becoming 
choked  with  carbon.  The  proper  oil  for  use 
in  a  gas-engine  cylinder  is  a  thin  lubricant 
which  will  not  carbonize  under  the  high 
temperatures  present  in  the  gas-engine 
cylinder.  Don't  think  that  because  steam- 
engine  cylinder  oil  costs  four  times  as  much 
as  gas-engine  cylinder  oil,  it  is  four  times 
as  good.  The  direct  opposite  is  true.  For 
an  engine  with  an  inclosed  crank-case  an- 
other special  oil  is  required  and  is  known 
to  the  trade  as  "  crank-case  oil."  Ordinary 
oils  will  churn  into  lumps  in  the  presence 
of  water  and  soon  become  practically  use- 
less as  a  lubricant. 

It  is  not  a  bad  practice  to  make  an  occa- 
sional examination  of  the  exhaust-passages 
in  order  to  determine  whether  they  have  an 
accumulation  of  carbon  in  the  form  of  soot. 
With  some  gases  this  deposit  does  not 
amount  to  a  great  deal,  while  with  others 
the  deposit  is  such  as  to  in  time  cause 
sufficient  back  pressure  to  materially  de- 
crease the  power  of  the  engine.  Should f 
the  water  used  for  cooling  purposes  contain 
substances  that  are  likely  to  cause  a  deposit 
of  sediment  in  the  water-jacket,  the  jacket 
should  be  cleaned  occasionally  by  means  of 
a  long  iron  rod  with  a  hook  on  the  end, 
similar  to  a  poker. 

29 


Examine  all  valves  occasionally,  paying 
particular  attention  to  the  exhaust-valve 
to  see  if  it  is  cutting.  If  they  show  the 
least  sign  of  leaking  they  should  be  at- 
tended to  at  once  and  ground  to  a  good  fit 
to  the  seat  with  flour  emery.  Never  neg- 
lect a  leaky  valve,  for,  once  started,  the  leak 
will  increase  rapidly  in  size.  Examine  the 
springs  frequently  to  see  that  they  pull  the 
valves  securely  to  their  seats.  This  can  be 
determined  by  taking  hold  of  the  valve- 
stem  and  pulling  it  back  from  its  seat.  The 
resistance  to  the  pull  should  be  a  stiff  one, 
even  at  the  start,  for  all  valves  excepting  a 
suction  inlet.  In  the  case  of  an  inlet-valve 
operated  by  the  suction  of  the  piston,  it 
should  respond  promptly  to  the  vacuum  in 
the  cylinder,  a  very  small  movement  of 
crank  past  the  center  causing  it  to  open. 
It  should  be  carefully  adjusted  so  that  it 
will  seat  firmly  and  yet  respond  promptly 
to  the  vacuum.  The  gas-valve  should  also 
receive  its  share  of  attention. 

With  engines  using  electric  ignition,  the 
care  of  the  igniter  mechanism  is  one  of  the 
most  important  points.  Never  neglect  the 
igniter.  Much  of  the  prejudice  against  the 
electric  igniter  is  the  result  of  improper 
care  of  the  ignition  apparatus.  In  case  a 
primary  cell  is  used  for  the  battery,  a  full 
set  of  renewals  should  be  kept  on  hand  at 

3° 


all  times  and  the  battery  should  be  renewed 
before  it  is  too  weak. 

In  case  an  ignition-tube  is  employed,  it 
pays  at  all  times  to  get  the  best  that  can  be 
obtained.  Nickel  alloy  is  much  the  best 
material  to  employ  for  this  purpose,  as  a 
tube  made  from  the  alloy  will  last,  with 
ordinary  care,  from  six  to  eighteen  months, 
according  to  the  work  the  engine  has  to 
perform.  Wrought-iron  tubes  have  to  be 
replaced  anywhere  from  every  two  days  or 
so  to  every  two  weeks.  The  shut-down  nec- 
essary while  replacing  a  tube  is  annoying, 
to  say  the  least,  and  it  may  cause  expensive 
delays.  A  new  tube  should  be  kept  in  stock 
at  all  times,  and  when  tubes  that  last  but  a 
short  time  are  used,  it  would  be  well  to  keep 
several  on  hand. 

Do  not  keep  the  tube  too  hot  at  any  time, 
as  a  high  temperature  reduces  its  strength 
and  makes  it  wear  out  so  much  sooner  than 
it  otherwise  would.  The  proper  tempera- 
ture to  keep  the  tube  is  at  a  bright  cherry, 
not  a  white  heat.  The  temperature  of  the 
tube  for  ignition,  will  vary  somewhat  with 
gas  of  different  qualities  and  the  engineer 
should  determine  for  himself  the  lowest 
temperature  at  which  the  tube  will  work 
successfully. 

If  at  any  time  the  engineer  has  forgotten 
to  turn  on  the  jacket  water  and  the  engine 


begins  to  throw  out  volumes  of  smoke 
through  the  open  end  of  the  cylinder,  turn 
on  the  jacket  water,  but  do  so  with  great 
caution,  as,  if  the  cylinder  walls  are  cooled 
too  rapidly,  the  cylinder  may  contract  be- 
fore the  piston  has  time  to  do  so,  and  it 
may  bind  the  piston  so  as  to  materially 
damage  the  engine.  The  cylinder  oil-cup 
^should  also  be  opened  wide  at  the  same 
time,  to  give  the  cylinder  an  excess  of  oil 
and  ward  off  the  possibility  of  its  binding. 

Feel  of  the  bearings  occasionally,  and 
keep  watch  of  the  sight  feed  of  the  oil-cups, 
so  that  no  injury  may  be  done  to  the  engine 
by  cutting  of  the  journals.  Don't  attempt 
to  cool  an  overheated  bearing  with  ice  un- 
less you  thoroughly  understand  what  you 
are  about.  You  may  get  an  effect  the  oppo- 
site of  that  desired,  and  find  that  the  sudden 
cooling  of  the  outside  of  the  bearing  has 
caused  it  to  grip  the  shaft  like  a  vise.  If 
the  ice  can  be  applied  to  the  shaft  itself  so 
as  to  cause  the  shaft  to  contract  before 
the  surrounding  metal,  all  trouble  may  be 
averted  and  the  desired  effect  obtained. 

Examine  the  governor  occasionally  to  see 
that  it  is  working  freely  and  is  not  clogged  by 
dirt  or  any  foreign  matter.  The  regularity 
of  motion  is  dependent  as  much  upon  the 
sensitiveness  of  the  governing  device  as 
upon  the  flywheel.  If  the  governor  is  a  hit- 

32 


aiid-niiss,  see  that  the  gas-valve  is  open  just 
far  enough  to  cause  an  explosion  to  follow 
immediately  upon  the  action  of  the  gov- 
ernor. Nearly  all  governors  of  this  type 
use  a  pick-blade,  and  if  the  gas  is  not  turned 
on  sufficiently,  the  blade  will  strike  or  let 
go  — according  to  its  method  of  operation 
—  some  time  before  the  engine  will  receive 
an  impulse,  and  the  consequence  is  a  slow- 
ing down  of  the  engine  until  the  mixture 
becomes  rich  enough  to  produce  an  ex- 
plosion. 

If  there  is  a  pet  cock  on  the  engine  having 
communication  with  the  compression  space, 
the  proper  state  of  the  mixture  may  be  de- 
termined by  opening  the  pet  cock  just  at  the 
time  of  ignition  and  observing  the  color  of 
the  flame.  If  the  flame  is  an  extremely  pale 
blue,  the  mixture  has  too  little  gas  and  the 
gas-valve  should  be  opened  a  little  wider. 
If,  on  the  other  hand,  the  flame  is  tinged 
with  red,  orange  or  yellow  the  mixture  is 
too  rich.  The  proper  color  of  the  flame  is 
a  deep  blue  approaching  a  violet.  Do  not 
depend  for  this  test  upon  a  pet  cock  situ- 
ated close  to  the  gas-valve  opening,  as  the 
mixture  at  this  point  of  the  compressior 
space  is  usually  much  richer  in  gas  than  at 
the  center. 

At  intervals  of  six  months,  if  the  engine 
is  in  constant  use,  remove  the  piston  anc 


clean  the  piston  and  the  inside  of  the  cylin- 
der with  kerosene.  Take  out  the  piston  - 
rings  and  give  them  and  the  grooves  in 
which  they  lie  a  thorough  cleaning  as  well. 
The  valve-stems  should  be  given  an  oc- 
casional spray  of  kerosene  with  a  squirt  can. 
Never  use  heavy  oil  for  this  purpose,  as  it 
will  cause  the  stem  to  clog  and  stick.  This 
is  especially  true  of  the  exhaust- valve  stem. 


34 


CHAPTER  VI. 

GAS-ENGINE  TROUBLES. 

While  it  is  not  possible  to  anticipate  ev 
ery  trouble  that  may  occur  in  the  running 
of  a  gas  engine,  a  general  outline  of  such 
troubles  as  are  of  frequent  occurrence,  and 
the  remedies  that  apply  in  each  case,  will 
give  a  clew  to  the  solution  of  those  prob- 
lems not  considered  in  this  chapter. 

Failure  to  Start.— See  first  that  the  fuel- 
valve  is  not  open  too  wide,  nor  that  it  has 
not  been  open  a  small  amount  for  a  length 
of  time  that  would  allow  an  excess  of  gas  or 
gasoline  to  leak  into  the  cylinder.  Then 
examine  the  igniter.  If  a  tube,  see  that  it  is 
not  too  cold.  If  an  electric  igniter,  look  it 
over  thoroughly  as  directed  in  the  chapter 
on  Starting.  See  if  the  gas  supply  is  inter- 
rupted in  any  way.  It  may  not  have  been 
turned  on.  In  cold  weather,  a  gasoline  en- 
gine may  fail  to  start  because  the  gasoline 
does  not  vaporize.  In  this  case,  warm  the 
air-inlet  pipe,  or  fill  the  water-jacket  with 

35 


hot  water.  In  very  severe  weather  it  is  a 
good  plan  to  do  both. 

Engine  Starts,  but  with  W'eak  Explo- 
sion.— The  igniter  may  be  set  too  late,  and 
it  should  be  adjusted  to  ignite  just  before 
the  engine  reaches  the  rear  dead  center  on 
the  compression  stroke.  The  fuel-valve 
may  not  be  open  wide  enough.  The  engine 
may  lose  compression  from  various  causes. 
One  or  both  of  the  valves  may  leak  or  may 
not  seat  itself  with  sufficient  force.  The 
starting  lever  may  be  still  in  the  starting 
position.  The  relief-cock  may  be  open. 
The  piston  may  leak,  but  this  is  not  often 
sufficient  to  materially  affect  the  power  of 
the  engine.  See  that  the  valve  springs  are 
not  too  weak. 

Explosions  in  the  Exhaust  Passages. — 
The  exhaust-valve  may  leak  or  may  not  seat 
property.  The  ignition-tube  is  too  cold,  or 
the  electric  spark  is  weak.  The  fuel -valve 
may  be  open  too  wide,  so  that,  occasionally, 
the  mixture  in  the  cylinder  is  too  rich  to  take 
fire.  The  primary  cause  of  this  trouble,  is 
always  the  occurrence  of  unburned  fuel  in 
the  exhaust  passages. 

Jingine  Slows  J)oicn  and  Finally  Stops. — 
This  may  be  due  to  overheating  of  the 
piston  or  the  cylinder,  because  of  an  insuffi- 
cient supply  of  water,  or  insufficient  oil.  One 
or  more  of  the  bearings  may  be  overheated. 

36 


notably  the  crankpin  or  the  crankshaft 
bearings.  The  engine  may  be  overloaded. 
See  also  the  comment  under  Weak  Explo- 
sion above.  For  the  treatment  of  an  over- 
heated cylinder  or  bearing,  read  the  chapter 
on  the  care  of  a  gas  engine.  See  paragraph 
on  "  Back  Firing." 

Explosions    Cease.  —  See    paragraph   on 
Failure  to  Start. 

Premature  Explosions,  "  Back  Firin^ 
This  trouble  is  of  most  frequent  occurrence 
with  fuel  of  a  low  ignition  temperature, 
such  as  gases  rich  in  hydrogen,  and  gaso- 
line. If  the  ignition  apparatus  is  properly 
adjusted,  the  source  of  the  trouble  may  be 
traced  to  an  overheated  cylinder  and  too 
high  compression,  or  to  highly  heated  pro- 
jections within  the  compression  space. 
The  latter  cause  of  this  annoying  trouble 
has  frequently  been  a  puzzle  for  some  of 
the  best  gas-engine  men  to  find.  A  thin 
projection  of  metal  within  the  cylinder 
may  be  so  situated  that  it  becomes  heated 
to  a  comparatively  high  temperature  and 
acts  in  the  same  manner  as  an  ignition-tube. 
Again,  there  may  be  a  projection  within 
the  cylinder  upon  which  carbon  will  deposit 
in  the  shape  of  a  cone.  This  cone  of  carbon 
will  become  incandescent,  or  nearly  so,  and 
cause  premature  ignition,  even  as  early  as 
on  the  suction  stroke.  Projections  upon 


the  piston  head  such  as  the  heads  of  fol- 
lower-bolts, nuts,  etc.,  quite  frequently 
make  trouble  in  this  way.  In  two-cycle 
engines  of  the  Day  type,  explosions  will 
sometimes  occur  in  the  crank-chamber 
because  of  an  insufficient  fuel  supply. 

Flame  Blown  Out. — If  in  engines  of  the 
Otto  slide  valve  type,  the  flame  is  frequently 
blown  out  and  there  is  no  draft  to  which 
this  trouble  may  be  traced,  it  is  a  sign  of 
a  leaky  slide  valve,  and  that  either  the 
springs  need  tightening  or  the  valve  itself 
needs  facing.  Should  the  flame  on  a  tube- 
igniter  be  blown  out,  there  is  a  leak  either 
in  the  tube  itself  or  in  some  surrounding 
part  of  the  engine. 

Spark  Gradually  Weakens. — A  spark  that 
is  of  the  proper  strength  when  the  engine 
is  started,  may  gradually  get  wreaker  after 
the  engine  is  running,  until  it  is  finally  too 
weak  to  ignite  the  charge.  If  the  spark  is 
furnished  by  a  battery,  this  is  a  sign  that 
the  cells  need  recharging  or  that  the  cell  is 
'  not  adapted  to  the  work.  Battery  cells  that 
are  made  for  open  circuit  only,  as  those  of 
the  sal-ammoniac  type,  are  un suited  for 
gas-engine  ignition,  because  they  polarize 
rapidly  and  there  is  not  sufficient  time  for 
them  to  recover  between  the  sparks.  Occa- 
sionally a  magneto  will  grow  weaker  after  a 
few  hours  use,  showing  that  the  magnets 


are  not  strong  enough  to  stand  the  work 
required  of  them.  The  remedy  is  to  get  a 
better  magneto. 

Engine  Pounds.  —  -Look  the  engine  over 
carefully  to  determine  if  there  are  any  loose 
bearings.  Lost  motion  is  the  prevalent 
cause  of  noise  in  any  machine  or  mechan- 
ism. If  the  bearings  are  "  snug,"  note  if 
the  igniter  has  too  much  lead,  or  if  prema- 
ture explosions  occur  from  any  other  cause. 

Engine  does  not  Develop  Full  Power. — 
Note  what  is  said  in  the  paragraph  on  Weak 
Explosion;  then,  if  the  trouble  be  not 
found,  see  if  the  exhaust  passages  are 
obstructed  in  any  way.  See  also  Engine 
Slows  Down. 

Smoke. — A  black  smoke  may  sometimes 
be  observed  issuing  from  the  open  end  of 
the  piston.  In  this  case  the  piston  is  leak- 
ing. The  remedy  will  suggest  itself,  upon 
taking  out  the  piston  and  examining  its 
condition.  If  the  cylinder  is  badly  out  of 
round  it  should  be  rebored.  The  packing 
rings  may  need  renewing.  See  if  they  are 
too  small  to  expand  to  a  size  slightly 
greater  than  the  bore  of  the  cylinder. 
Smoke  from  the  open  end  of  the  cylinder 
may  also  come  from  overheating.  Smoke 
issuing  from  the  exhaust-pipe,  is  due  to  an 
excess  of  fuel  in  the  mixture. 

Leaks. — To  stop  a  leak  at  any  point  about 

19 


the  engine,  first  try  tightening  up  the  bolts 
or  nuts  that  hold  the  parts.  If  this  does 
not  stop  the  trouble,  and  the  joint  is 
packed,  renew  the  packing.  Should  the 
joint  be  a  ground  joint,  it  should  be  re- 
ground  with  flour  emery  and  oil,  and  the 
joint  wiped  perfectly  clean  after  the  opera- 
tion. The  best  remedy  for  a  leaky  valve- 
stem  is  to  ream  out  the  bearing  and  put  in 
a  bushing  or  a  larger  stem,  being  careful  to 
see  that  the  stem  is  in  line  when  the  job  is 
complete,  and  that  the  bearing  centers  with 
the  valve  seat. 


40 


CHAPTER  VII. 

GASOLINE    ENGINES. 

In  general  details  and  appearance,  there 
is  little  to  distinguish  between  the  gas 
engine  and  the  gasoline  engine.  The  only 
point  of  difference  being,  that  a  gasoline 
engine  has  a  special  attachment  for  the 
purpose  of  supplying  fuel  to  the  engine 
cylinder,  either  in  the  form  of  vapor  or  a 
finely  .divided  spray.  In  engines  where  the 
compression  within  the  cylinder  is  carried 
to  the  practical  limit,  it  is  found  that  the 
limit  is  a  somewhat  lower  pressure  for 
gasoline  than  for  gas  of  the  average  quality 
employed  for  a  gas-engine  fuel.  A  gasoline 
engine  will  develop  more  power  than  can 
be  obtained  from  the  same  engine  using  a 
good  quality  of  natural  gas.  A  mixture  of 
gasoline  and  air  will  become  entirely  ignited 
in  much  less  time  than  a  mixture  composed 
of  air  and  gas.  This  peculiarity  of  gasoline 
produces  a  much  more  powerful  blow  at 
the  beginning  of  the  power  stroke,  and 


usually  causes  the  indicator  to  show  a  much 
higher  pressure  at  this  point  than  is  prob- 
ably present  in  the  engine  cylinder,  owing 
to  the  inertia  of  the  pencil  mechanism 
being  too  great  to  allow  it  to  stop  when  the 
maximum  pressure  is  reached.  A  study  of 
gasoline-engine  indicator  diagrams  will 
show  this  effect,  as  illustrated  in  Chapter 
XIV. 

Devices  for  supplying  gasoline  to  the 
engine,  may  be  divided  into  three  classes; 
carbureters,  vaporizers  and  jets. 

A  carbureter  is  a  device  for  transforming 
liquid  fuel  into  a  vapor  by  passing  air  either 
over  or  through  a  body  of  the  liquid,  and 
carrying  off  a  portion  of  the  liquid  in  the 
form  of  vapor  with  the  air.  Carbureters 
usually  operate  at  ordinary  temperatures, 
but  for  fuels  that  have  a  low  specific  gravity 
the  air  or  the  fuel  and  sometimes  both,  are 
heated.  This  mixture  of  gas  and  air  is 
usually  too  rich  in  fuel  to  be  explosive,  and 
a  further  addition  of  air  in  the  engine 
cylinder  is  required  before  it  is  suited  to 
the  wrork. 

A  vaporizer  is  an  appliance  for  transform- 
ing into  vapor,  just  the  quantity  of  gasoline 
that  is  required  for  one  impulse  of  the 
engine  and  no  more,  and  it  differs  from  the 
carbureter  in  not  having  a  supply  of  vapor 
constantly  on  hand.  Either  the  proper 

42 


*H* 


Fig.  4. 


quantity  of  fuel  is  caused  to  flow  directly 
into  the  path  of  the  entering  air,  or  the  air 
is  passed  over  a  pipe  connecting  with  a 
small  gasoline  reservoir  and  a  current  of 
the  fuel  is  induced  into  the  path  of  the 
entering  air. 

Jets  are  what  the  name  implies,  a  jet  of 
liquid  usually  controlled  by  a  small  pump. 
The  pump  throws  a  jet  of  the  liquid  into 
the  air  pipe  so  that  it  strikes  the  side  of  the 
pipe  and  breaks  into  a  spray,  or,  as  in  cer- 
tain classes  of  kerosene  engines,  into  a 
compartment  of  the  compression  space  and 
against  the  side.  Jets  are  sometimes  classed 
as  vaporizers,  but  placing  them  in  a  class 
by  themselves  makes  them  much  more  con- 
venient to  refer  to. 

Carbureters  may  be  divided  into  two 
classes,  surface  carbureters  and  Jittering 
carbureters. 

In  Fig.  4  is  shown  an  example  of  a  surface 
carbureter.  The  carbureter  is  constructed 
in  the  form  of  a  spiral  in  order  that  the  air 
passage  through  it  may  be  a  long  one.  The 
bottom  of  the  carbureter  is  covered  with 
gasoline  to  the  height  ,rjy,  and  the  wicking 
ww  absorbs  the  liquid  so  that  a  large  sur- 
face of  fuel  is  exposed  to  the  air  as  it  passes 
through.  According  to  Mr.  Gardner  His- 
cox,  the  height  of  the  gasoline  should  be 
not  over  3  inches  and  the  total  height  of 

44 


p 


Fig.  5- 

4.S 


the  carbureter  not  over  8  inches.  The  air 
enters  the  spiral  through  the  clack-valve  v 
and  passes  to  the  engine  through  the  pipe  e. 

A  filtering  carbureter  is  shown  in  Fig.  5. 
The  air  enters  the  carbureter  through  the 
holes  h  and  passes  downward  through  the 
pipe  p  to  the  gasoline,  whence  it  bubbles 
up  carrying  with  it  particles  of  vapor.  A 
float  F  carries  the  pipe  p  in  order  that  the 
lower  end  may  be  constantly  at  the  same 
distance  below  the  surface  of  the  liquid.  In 
passing  upward,  the  carbureted  air  goes 
through  the  wire  gauze  g  so  any  drops  of 
the  fuel  that  may  be  held  in  suspension  will 
be  caught  and  left  behind.  The  mixture 
passes  to  the  engine  through  the  pipe  e. 

A  good  example  of  a  vaporizer  is  shown 
in  Fig.  6.  Gasoline  enters  the  vaporizer 
through  the  needle  valve  n  and  air  through 
an  opening  leading  to  the  space  A.  The 
double-seated  valve  A  is  lifted  at  each  in- 
duction stroke  of  the  engine,  the  larger 
seat  opening  a  passage  for  the  mixture 
while  the  smaller  seat  on  lifting  opens  the 
passage  for  the  gasoline.  As  the  air  is 
warmed  previously  to  coming  in  contact 
with  the  fuel,  it  vaporizes  readily,  and  the 
proportions  of  gasoline  vapor  and  air  may 
be  regulated  by  the  needle  valve. 

An  example  of  the  jet  is  shown  and 
described  in  Chapter  IX,  see  Fig.  9.  The 

46 


Fig.  6. 


47 


method  explained  in  that  chapter  is  one  in 
use  in  an  oil  engine  and  a  similar  feed  is 
used  with  a  gasoline  engine,  with  the  excep- 
tion that  the  jet  is  thrown  into  the  air-inlet 
pipe,  usually  against  the  side. 


157 


CHAPTER  VIII. 

HANDLING  A  GASOLINE  ENGINE. 

For  starting,  stopping  and  the  care  of  a 
gasoline  engine,  the  same  general  rules 
apply  as  for  a  gas  engine.  In  starting  a 
gasoline  engine,  especially  when  the  engine 
is  cold  after  standing  idle  for  some  time,  it 
is  a  good  plan  to  put  a  quantity  of  gasoline 
in  the  cylinder  and  allow  it  to  remain  there 
for  about  a  minute  before  starting  the  en- 
gine. With  engines  employing  a  pump  to 
raise  the  gasoline  from  a  tank  or  reservoir, 
it  is  necessary  to  operate  the  pump  by  hand 
for  a  few  strokes  in  order  to  get  a  supply  of 
fuel  in  the  reservoir.  The  fuel  supply  to  the 
engine  is  usually  regulated  by  means  of  a 
needle  valve,  which  should  be  carefully 
cleaned  at  regular  interval-s.  In  engines 
using  a  jet  feed,  the  supply  is  regulated  by 
adjusting  the  stroke  of  the  pump,  or  by 
regulating  the  opening  in  a  by-pass,  so  that 
a  portion  of  the  fuel  is  pumped  through 
the  by-pass  and  returns  to  the  source  of 
supply. 

49 

HTCov. 


With  engines  using  a  carbureter,  it  may 
be  found  necessary,  in  extremely  cold 
weather,  to  arrange  some  means  of  supply- 
ing heat  to  it,  because  the  transformation 
of  the  fuel  into  vapor  produces  a  refriger- 
ating effect  which  will  chill  the  liquid  to 
such  an  extent  that  it  will  not  vaporize. 
Two  methods  of  heating  the  carbureter  may 
be  employed ;  one  is  to  pass  the  exhaust- 
pipe  through  the  liquid  and  the  other  is  to 
warm  the  fuel  by  means  of  the  outgoing 
jacket  water.  The  latter  method  is  un- 
doubtedly the  most  satisfactory  as  it  avoids 
•excessive  heating  of  the  gasoline.  In  kero- 
sene-oil engines  which  operate  on  the  car- 
bureter or  vaporizer  principle,  it  is  found 
.absolutely  necessary  to  heat  the  fuel  before 
it  enters  the  cylinder.  In  some  forms  of 
jet  supply,  it  is  not  necessary  to  heat  the 
kerosene  before  it  enters  the  cylinder,  as  it 
is  either  injected  against  a  highly  heated 
surface  or  into  a  body  of  air  that  has  been 
brought  to  a  high  temperature  by  compres- 
sion, as  in  the  Diesel  motor. 

The  time  of  ignition  in  the  gasoline 
engine  may  be  made  a  little  later  in  the 
cycle,  and  thus  avoid  the  hard  blow  pro- 
duced at  the  time  of  the  explosion,  without 
a  noticeable  loss  in  power.  In  starting  a 
gasoline  engine,  it  is  often  necessary  to 
iirst  keep  the  regulating  valve  entirely 

50 


closed  and  to  open  it  a  little  at  a  time 
immediately  after  the  engine  receives  its 
first  impulse.  In  general,  a  carbureter  will 
produce  a  more  perfect  mixture  than  the 
jet  or  the  vaporizer,  thus  insuring  complete 
combustion  and  a  consequent  absence  of 
smoke  and  odor  at  the  exhaust.  But  this 
advantage  is,  in  many  engines,  offset  by  the 
many  disadvantages  of  this  method. 

The  carbureter  usually  takes  but  the 
lighter  portions  of  the  fuel,  leaving  in  the 
bottom  of  the  tank  a  residue  which  is  of 
little  or  no  value,  as  it  is  of  too  low  a 
specific  gravity  to  be  used  as  a  fuel  in  the 
engine.  On  the  other  hand,  the  vaporizer 
or  the  jet  insures  the  using  of  all  the  fuel 
irrespective  of  specific  gravity,  if  the  aver- 
age of  the  mixture  is  equal  to  that  required 
by  the  engine.  In  the  occasion  of  the 
engine  being  located  near  a  refinery,  it  is 
probable  that  the  residue  resulting  from 
the  use  of  a  carbureter  may  be  sold  at  a 
price  that  will  overcome  that  objection  to 
this  method.  In  general,  however,  the 
vaporizer  or  jet  will  be  found  the  least 
troublesome,  although  some  very  successful 
engines  are  employing  carbureters. 

At  no  time  should  there  be  any  foreign 
matter  permitted  to  enter  the  gasoline- 
supply  pipes  or  the  valves.  Gasoline  tanks 
should  be  filled  through  a  fine-wire  strainer 


or  a  piece  of  closely  woven  muslin.  The 
opening  of  the  supply-pipe  into  the  tank 
should  be  covered  with  a  strainer  and  every 
precaution  taken  to  prevent  trouble  from 
this  source.  Never  put  the  gasoline  in 
anything  but  a  perfectly  clean  receptacle. 
Old  paint  or  varnish  cans  or  barrels  are 
especially  to  be  avoided.  At  regular  inter- 
vals, drain  the  gasoline  tank  and  clean  it 
thoroughly.  Where  the  tank  is  under 
ground  or  in  a  similar  position,  in  which 
it  would  be  impractical  to  clean  it,  extra 
precaution  should  be  taken  to  avoid  the 
entrance  of  foreign  matter.  Much  of  the 
trouble  experienced  with  gasoline  engines 
occurs  from  neglect  of  this  precaution. 

Large  quantities  of  gasoline  should  be 
stored  at  some  distance  from  buildings, 
and  the  tank  should  be  protected  from  the 
direct  rays  of  the  sun  by  means  of  a  shed  or 
a  covering  of  earth.  If  the  tank  is  made  of 
sheet  iron  and  fitted  with  a  safety  valve 
that  will  allow  the  escape  of  the  vapor,  so 
that  the  pressure  induced  by  overheating 
may  be  relieved  before  endangering  the 
tank,  much  of  the  loss  by  evaporation  will 
be  avoided.  Many  gasoline-tank  explosions 
are  due  to  excessive  pressure  caused  by  the 
overheating  of  a  tightly  closed  receptacle, 
and  not  from  the  application  of  a  flame. 
Usually,  the  evaporation  of  this  light 


hydrocarbon  is  so  rapid  that  all  air  is 
driven  from  the  vacant  space  above  the 
liquid  and  a  flame  applied  to  an  outlet  of 
the  tank  would  not  cause  an  explosion,  as 
the  mixture  would  be  too  rich. 

If,  by  any  mishap,  a  tank  of  gasoline  takes 
fire  at  a  small  outlet,  run  to  the  tank  and 
not  away  from  it,  and  either  blow  or  pat  the 
flame  out.  Never  put  water  on  burning 
gasoline  or  oil,  for  the  oil  will  float  on  top 
of  the  water  and  the  flames  spread  so  much 
the  more  rapidly.  Throw  fine  earth,  sand 
or  flour  on  top  of  the  burning  liquid.  Flour 
is  best,  because  it  will  float  and  less  will  be 
needed.  The  best  fire-extinguisher  for  a 
fire  of  this  sort  in  a  room  that  may  be 
closed  is  ammonia.  Several  gallons  of 
ammonia,  thrown  in  the  room  with  such 
force  as  to  break  the  bottles  which  contain 
it,  will  soon  smother  the  strongest  fire  if 
the  room  be  kept  closed.  Very  often, 
simply  striking  the  opening  from  which 
the  flame  is  issuing,  with  the  palm  of  the 
hand  will  put  out  the  fire. 


CHAPTER  IX. 

IGNITERS. 

A  good  igniter  is  one  of  the  most  impor- 
tant parts  of  a  gas  engine.     It  is  required 
of  an    igniting    device:    that   it    shall   fire 
every   charge   without    fail,    that    it    shall 
ignite  the  charge  at  the  proper  point  of  the 
cycle,  and  that  it  shall  require  a  minimum 
amount  of  attention  both  for  cleaning  and 
renewal  of  parts.     There  are  four  distinct 
ways  in  which  the  charge  may  be  ignited 
I.     Ignition  by  means  of  a  naked  flame. 
II.     Contact  with  a  surface  which  is  at 
high  temperature. 

III.  The  flame  of  a  small  electric  arc. 

IV.  Raising  the  temperature  of  the  cylin- 

der contents  by  high  compression. 
Flame  ignition  has  its  best  known  example 
in  the  Otto  slide-valve  engine.  The  general 
principle  involved  is,  however,  much  better 
illustrated  in  Barnett's  igniting  cock,  Fig. 
7.  In  this  method  of  ignition  two  gas  jets 
are  necessary.  One,  the  flame  f  which  is 

54 


Fig.  7. 


55 


employed  for  ignition  of  the  charge,  and 
the  other  F  for  relighting^"  when  blown  out 
by  the  explosion  within  the  cylinder.  The 
plug  valve  A  is  shown  in  the  proper  posi- 
tion for  relighting  the  flame  f.  At  the  right 
moment,  the  valve  makes  a  quarter  turn  so 
that  the  opening  in  the  plug  is  opposite 
the  opening  into  the  cylinder  indicated  by 
the  dotted  lines.  The  resulting  explosion 
extinguishes  the  flame  f,  and  the  valve  .re- 
turns to  the  position  shown  in  the  figure, 
the  gas  rushes  out  through  the  opening  and 
ignites  at  the  flame  F. 

Contact  with  a  highly  heated  surface 
finds  its  best  example  in  the  hot  tube.  In 
several  makes  of  kerosene  oil  engines,  a 
portion  of  the  cylinder  is  divided  from  the 
remainder  by  a  narrow  passage  and  left 
unjacketed,  so  that  it  reaches  a  tempera- 
ture sufficiently  high  to  ignite  the  charge. 
Another  plan,  due  to  Mr.  Dugald  Clerk,  is 
to  drive  the  charge  through  a  grate  built  of 
thin  strips  of  platinum.  The  grate  is 
brought  to  the  proper  temperature  by 
means  of  an  exterior  flame  before  the 
engine  is  started  and,  thereafter,  the  grate 
receives  sufficient  heat  from  the  burning 
gases  to  ignite  the  following  charge.  This 
method  is  useless  in  a  hit-and-miss  type  of 
engine,  because  a  few  idle  strokes  will  allow 
the  grate  to  cool  to  a  temperature  below 

56 


57 


that  necessary  for  ignition.  Thin  rods  and 
even  small  bolts  have  been  employed  in 
much  the  same  manner  as  the  platinum 
grate. 

The  earlier  tube  igniters  used  what  is 
known  as  a  timing  valve.  This  valve 
opened  communication  with  the  tube,  so  as 
to  time  the  ignition  at  the  proper  point  of 
the  cycle.  It  is  now  the  common  practice 
to  time  the  firing  point  automatically  by 
the  compression  of  the  charge.  When  the 
engine  exhausts,  the  pressure  within  the 
tube  falls  to  that  of  the  atmosphere,  and  it 
is  filled  with  the  products  of  combustion. 
When  the  engine  compresses  a  fresh  charge, 
a  portion  of  the  mixture  is  driven  into  the 
ignition  tube,  forcing  the  products  of  com- 
bustion ahead  of  it,  and  when  the  pressure 
within  the  cylinder  has  reached  the  right 
amount,  the  fresh  mixture  is  brought  into 
contact  with  the  heated  portion  of  the  tube 
and  ignites.  A  tube  of  this  kind  with 
adjustable  burner,  is  shown  in  Fig.  8.  The 
tube  is  shown  at  t,  and  it  should  be  of 
either  nickel  alloy  or  porcelain.  The  gas 
is  driven  by  the  compression  of  the  piston 
into  the  tube  through  the  port  p.  The  tube 
is  heated  by  the  Bunsen  burner  b,  the  flame 
entirely  surrounds  the  tube  and  is  confined 
by  means  of  the  chimney  c.  The  chimney 
is  lined  with  a  tube  of  asbestos,  the  asbestos 


being  an  important  addition,  as  it  prevents 
the  heat  from  being  carried  off  through  the 
walls  of  the  chimney.  Minute  adjustments 
of  the  flame  may  be  obtained  by  swinging 
the  burner  b  about  the  set-screws  s,  while 
for  larger  movements  the  chimney  and  the 
burner  may  be  changed  by  loosening  the 
screw  y  and  sliding  the  chimney  along  the 
rod  r.  A  pet-cock  is  provided  at  g  for 
blowing  the  soot  from  the  tube.  In  general 
the  flame  and  the  chimney  are  not  made 
adjustable,  their  proper  position  having 
been  determined  by  experiments  at  the 
factory,  and  the  chimney  and  burner  being 
fastened  in  the  position  found  most  favora- 
ble for  the  operation  of  the  engine. 

Ignition  by  contact  with  a  hot  surface  in 
the  combustion  chamber,  is  illustrated  in 
Fig.  9.  This  set  of  diagrams  shows  the 
series  of  operations  which  take  place  in  the 
Hornsby-Akroyd  oil  engine.  Before  start- 
ing the  engine  the  chamber  c  is  brought  to 
a  temperature  very  nearly  that  of  a  red  heat 
and  this  temperature  is  afterwards  main- 
tained by  the  combustion  within  the  cylin- 
der. During  the  suction  stroke  of  the 
engine,  a  jet  of  oil  is  forced  into  r  by  means 
of  a  pump  and,  striking  the  hot  surface  of 
the  chamber,  it  is  transformed  into  vapor. 
The  cylinder  of  the  engine  when  the  piston 
is  at  the  end  of  the  suction  stroke  contains 

59 


pure  air,  while  the  chamber  c  is  filled  with 
oil  vapor  and  products  of  combustion  left 
from  the  last  cycle.  In  the  figure,  the  oil 
is  represented  by  small  circles  and  the  air 
by  crosses,  while  the  products  of  combus- 
tion are  shown  by  small  squares.  In  dia- 
gram (B)  the  piston  has  compressed  the  air, 
driving  it  into  c  and,  as  soon  as  the  con- 
tents of  the  chamber  is  of  an  explosive 
nature,  it  takes  fire  from  the  heated  surface 
of  c.  In  diagram  (D)  the  piston  has  started 
on  a  forward  stroke,  expanding  the  products 
of  combustion. 

The  electric  igniter  is  slowly  but  surely 
taking  the  place  of  all  others,  because  only 
by  its  use  can  the  ignition  of  the  charge  be 
timed  to  a  certainty.  The  form  of  electric 
igniter  which  is  in  most  general  use,  op- 
erates upon  the  following  principle:  An 
electric  circuit  from  a  battery  or  other 
source  of  electrical  energy  is  closed,  by 
means  of  contact  points  within  the  com- 
pression space,  through  an  inductive  resist- 
ance in  the  form  of  a  spark  coil.  Upon 
breaking  the  circuit,  the  inertia  produced 
by  the  induction  raises  the  pressure  of  the 
circuit  and  causes  a  hot  spark  to  arc  across 
the  terminals.  This  method  is  known  as 
the  make-aiid-break,  and  it  may  be  pro- 
duced either  by  forcing  the  two  contacts  to- 
gether and  then  throwing  them  suddenly 

61 


00- 


Fig.  10. 


apart  by  means  of  a  spring,  or  by  wiping  one 
contact  on  the  other  in  a  manner  that  is 
known  as  the  wipe  break.  This  latter 
method  produces  a  very  hot  spark,  but  pro- 
vision must  be  made  for  adjustment  as  the 
points  wear  out  quite  rapidly. 

In  either  method,  good  judgment  must 
be  used  in  adjusting  the  current  supply  to 
the  requirements  of  the  ignition  device. 
Too  little  pressure  will  produce  but  unsat- 
isfactory ignition,  while,  should  the  pres- 
sure be  such  that  the  current  will  be  large, 
the  contact  points  will  wear  out  in  a  very 
short  time.  Where  the  battery  employed 
is  of  low  resistance,  as  in  the  case  of  a 
storage  cell,  the  pressure  at  the  battery 
terminals  should  be  much  less  than  with 
cells  having  a  high  internal  resistance. 
Two  methods  are  available  for  reducing  the 
rapid  destruction  of  the  points  by  too  large 
a  flow  of  current,  when  it  is  inadvisable  to 
reduce  the  number  of  cells.  The  destruct- 
ive action  of  the  spark  may  be  annulled  by 
placing  a  condenser  in  parallel  with  the 
break  as  shown  in  Fig.  10,  or  by  putting  a 
noninductive  resistance  in  series  with  the 
circuit  as  shown  in.  Fig.  loa.  To  make  a 
noninductive  resistance,  wind  the  wire  in  a 
coil,  about  a  core  that  contains  110  iron,  and 
begin  to  wind  at  the  center  of  the  length  of 
wire  so  that,  when  finished,  one  half  the 

63 


64 


current  will  flow  in  one  direction  around 
the  coil,  and  the  remaining  half  in  the 
opposite  direction.  If  the  resistance  coil  is 
not  made  iioninductive,  it  will  be  quite 
sure  to  destroy  the  sparking  power  of  the 
spark-coil. 

An  example  of  the  first  style  of  make- 
and-break  is  shown  in  Fig.  n.  This  figure 
is  diagrammatic  only  and  is  not  intended  to 
represent  any  special  make  of  igniter.  From 
a  source  of  energy  B,  one  wire  is  grounded 
on  the  frame  of  the  engine.  The  other  side 
of  the  circuit  is  attached  to  the  insulated 
electrode  e,  and  it  contains  the  spark  coil  c 
connected  in  series.  The  cam  C,  rotated  in 
the  direction  of  the  arrow,  depresses  the 
spring  s  which  carries  with  it  the  electrode 
p  until  the  point  of  p  meets  e.  Further 
rotation  of  the  cam  merely  deflects  the 
spring,  increasing  the  pressure  between  the 
contacts.  Still  further  rotation  of  the  cam 
allows  the  end  of  the  spring  to  slip  off  the 
lip  and  it  flies  back,  carrying  with  it  the 
plunger  />,  making  a  quick  break  between 
the  contacts  and  producing  the  spark.  In 
practice,  much  trouble  is  experienced  with 
flat  springs  as  they  are  more  liable  to  break 
than  are  helical  springs.  Note  that  by 
helical  spring  is  meant  a  spring  that  is 
wound  in  the  form  of  a  screw  thread  as 
shown  at  A,  Fig.  12.  This  form  of  soring  is 

65 


bfl 

s 


66 


:>ften  but  erroneously  called  a  spiral  spring. 
The  true  spiral  spring  is  shown  at  B  in  the 
figure,  and  is  of  the  kind  so  much  used  in 
clocks ;  it  is  not  so  reliable  as  the  helical 
spring. 

An  example  of  a  wipe  break  is  shown  in 
Fig.  13.  The  electrodes  X  and  Y  are  so 
placed  that  they  lie  directly  in  the  path  of 
the  incoming  gases  in  order  to  keep  the 
electrodes  cool.  The  electrode  Fis  rotated 
by  the  crank  E,  and  rubs  against  the  spring 
electrode.  The  rubbing  has  the  advantage 
that  it  keeps  the  contact  surfaces  always 
clean.  The  electrode  Fis  made  adjustable, 
so  that  it  can  be  pushed  further  into  the 
valve  box  as  it  wears  off.  A  very  hot  spark 
is  produced  by  this  form  of  break  and,, 
although  it  requires  more  frequent  adjust- 
ment and  renewal  of  parts  than  some  other 
forms,  there  is  no  platinum  used,  so  that  it 
is  quite  a  favorite  with  some  designers.  It 
should  be  borne  in  mind  by  the  designer 
that,  in  both  these  forms  of  make-and- 
break  igniters,  contact  must  be  made  with 
pressure  and  the  break  must  be  a  quick 
one. 

Another  method  of  electric  ignition  that 
is  finding  great  favor,  especially  among 
automobile  builders,  is  the  jump-spark. 
This  spark  is  so  called  because  it  will  arc 
or  "jump"  across  an  air  gap  without  pre- 

67 


68 


viously  bringing  the  terminals  into  contact. 
It  is  produced  by  means  of  an  induction 
coil,  or  a  RuhmkorfF  coil  as  it  is  sometimes 
called.  In  this  coil  there  are  two  windings, 
one  of  comparatively  coarse  wire  wound  on 
a  core  of  iron  wire,  and  a  coil  of  much  finer 
wire  wTound  on  the  outside  of  the  coarse- 
wire  coil.  The  current  from  the  source  of 
energy  is  allowed  to  flow  through  the 
coarse  or  primary  winding,  and  any  varia- 
tion in  the  strength  of  the  primary  circuit 
will  induce  a  current  in  the  fine  wire  form- 
ing the  secondary  circuit.  In  a  Ruhmkorff 
coil  the  secondary  current  is  usually  pro- 
duced by  rapidly  opening  and  closing  the 
primary  circuit,  either  by  means  of  a 
magnetic  vibrator  or  by  a  toothed  wheel. 
This  method  produces  a  series  of  sparks 
across  any  gap  in  the  secondary  circuit  that 
is  not  too  great  for  the  capacity  of  the  coil. 
Sparks  are  produced  both  on  closing  the 
primary  circuit  and  when  it  is  broken,  but 
the  spark  at  the  break  is  much  the  more 
powerful  of  the  two.  The  induction  coil  is 
used  in  two  ways.  In  one  the  vibrator  is 
employed  and,  upon  closing  a  switch  on 
the  cam  shaft,  a  series  of  sparks  is  sent 
across  the  spark  gap  in  the  combustion 
space.  In  the  other,  110  vibrator  is  used, 
and  two  sparks  are  produced,  one  on  the 
opening  and  one  on  the  closing  of  the 

69 


b/J 
S 


switch.  The  second  spark  is  that  which  is 
depended  upon  for  igniting  the  charge,  as 
the  make  spark  is  not  strong  enough. 

The  arrangement  of  the  circuits  for  pro- 
ducing the  jump-spark  is  shown  in  Fig.  14. 
The  primary  circuit  passes  through  the 
switch  S  on  the  cam  shaft  to  the  primary  of 
the  coil,  through  the  primary  and  thence 
back  to  the  source  of  energy  B.  The  sec- 
ondary circuit  is  from  the  terminal  a  of  the 
secondary  to  the  terminal  x  of  the  ignition 
plug  and  from  the  terminal  y  of  the  ignition 
plug  to  the  terminal  b  of  the  secondary. 
For  the  secondary  circuit,  the  secondary 
winding  of  the  coil  becomes  the  source  of 
energy.  If  there  is  a  vibrator  in  the  circuit, 
the  time  of  ignition  will  be  immediately 
after  the  switch  closes  the  circuit.  If  there 
is  no  vibrator  in  the  circuit,  the  time  of 
ignition  will  be  just  as  the  switch  breaks 
the  circuit.  To  get  a  sure  ignition,  it  has 
been  found  that  the  points  should  be  set  a 
distance  apart  equal  to  about  one  quarter 
the  maximum  sparking  distance  of  the  coil. 
A  3^-inch  coil  with  a  J^-inch  gap  has  been 
found  to  give  very  good  results.  There  are 
coils  on  the  market  designed  expressly  for 
gas  engines  using  the  jump-spark,  and  the 
author  strongly  advises  the  reader  to  buy  a 
coil  rather  than  attempt  to  make  it  himself; 
for  the  reason  that  considerable  skill  and 


experience  is  requisite  for  the  design  and 
construction  of  a  coil  which  will  stand  the 
hard  service  required  of  it  when  used  for 
gas-engine  ignition. 

Raising  the  temperature  of  the  cylinder 
contents  is  a  method  that  has  proven  quite 
successful  in  the  Diesel  motor,  and  for  a 
description  of  this  method  the  reader  is 
referred  to  Chapter  I. 


72 


CHAPTER  X. 

VAI^VK  MECHANISMS. 

The  usual  form  of  valve  used  in  a  gas 
engine  is  that  known  as  the  mushroom 
type  and  is  shown  in  Fig.  29,  Chapter  XVII, 
where  the  general  proportions  of  the  valve 
are  treated.  The  reason  that  this  type  of 
valve  is  best  for  the  gas  engine,  is  because 
there  are  no  rubbing  surfaces  and  there  is 
very  little  wear.  The  high  temperature 
within  the  cylinder  of  the  gas  engine, 
makes  it  difficult  to  keep  the  valves  and 
their  seats  at  a  pressure  at  which  they  will 
wear  for  any  reasonable  length  of  time. 
Hot  gases  of  themselves,  when  passing  at  a 
high  rate  of  speed  through  a  small  opening, 
score  the  metal  surrounding  the  opening, 
and,  for  this  reason,  if  a  hole  is  once  started 
it  enlarges  rapidly  and  soon  the  engine  is 
not  working  at  its  full  power. 

In  nearly  all  gas  engines  of  the  four-cycle 
pe,  the  valves   are  operated  by  means  of 
ams  on  a  shaft  called  the  lay-  or  camshaft, 

73 


which  makes  one  revolution  to  two  of  the 
crankshaft.  Occasionally  the  use  of  the 
camshaft  is  avoided  by  employing  as  pecial 
mechanism  in  connection  with  an  eccentric, 
in  which  the  eccentric  rod  is  made  to  open 
the  valve  at  every  other  stroke,  the  interme- 
diate strokes  being  idle  ones.  In  an  engine 
manufactured  in  England,  a  rotating  valve 
is  employed  which  is  on  a  shaft  making 
one  revolution  to  four  revolutions  of  crank- 
shaft. The  valve  ports  are  so  arranged 
that  they  are  open  to  the  cylinder  twice  in 
each  revolution  of  the  valve-shaft. 

In  many  small  engines,  only  the  exhaust 
valve  is  opened  by  mechanical  means,  the 
inlet  valve  being  operated  by  the  suction 
of  the  engine.  This  of  necessity  causes 
some  wire-drawing  during  the  suction 
stroke,  as  there  must  be  a  partial  vacuum 
in  the  cylinder  before  the  valve  will  operate. 
On  large  engines,  wherein  a  small  propor- 
tionate loss  of  power  becomes  of  impor- 
tance, it  is  not  advisable  to  employ  the 
suction  valve,  and  the  inlet  valve  should 
be  operated  in  the  same  manner  as  the 
exhaust  valve.  In  fact,  some  gas-engine 
designers  claim  that  a  suction  valve  will 
give  trouble  because,  if  it  sticks  at  all,  the 
valve  opening  is  sure  to  be  reduced,  while 
with  a  mechanically  operated  valve,  a  little 
extra  friction  is  of  no  consequence.  There 

74 


75 


are,  however,  some  very  good  engines  and 
a  few  large  ones  which  have  been  operating 
for  several  years- with  suction  valves.  The 
only  advantage  the  author  can  see  in  such 
a  valve  is  simplicity  and  less  first  cost,  be- 
cause of  the  absence  of  the  valve  mech- 
anism. 

In  two-cycle  engines  of  the  Day  type,  the 
only  valve  required  for  either  the  exhaust 
or  the  inlet,  is  a  check-valve  opening  into 
the  crank-chamber.  For  a  description  of 
this  engine  and  the  valve  arrangement  the 
reader  is  referred  to  Chapter  I.  The  check- 
valve  will  cause  a  slight  wire-drawing  in 
the  crank-chamber,  but,  with  a  properly 
proportioned  engine,  there  is  no  vacuum 
formed  in  the  cylinder  at  any  portion  of  the 
stroke. 

It  is  customary,  in  the  design  of  a  valve 
mechanism,  to  transmit  motion  from  the 
cam  to  the  valve-stem  by  means  of  a  lever 
in  order  to  avoid  cramping  of  the  valve- 
stem  in  its  bearings.  If,  however,  the 
valve-stem  be  given  a  bearing  near  the  cam 
with  a  long  surface  and  the  stem  be  en- 
larged if  necessary  in  order  to  stiffen  it,  the 
intermediate  lever  may  be  omitted.  A  valve- 
operating  device  with  a  lever  is  shown  in 
Fig.  15.  The  lever  L  is  pivoted  at  x  and 
carries  the  roller  r  which  bears  against  the 
cam  C.  The  center  of  gravity  of  the  lever 

76 


L  is  placed  far  enough  to  the  right  of  x 
that  the  lever  will  incline  toward  the  cam 
after  it  has  been  thrust  by  the  valve -stem  s 
as  far  as  allowed  by  the  head  of  the  valve. 
The  hardened  steel  contact  piece  a  is  put 
in  the  end  of  the  valve-stem  and  a  hard- 
ened plate  b  is  dovetailed  into  the  lever. 

In  Fig.  16  is  shown  a  valve-stem  without 
the  lever.  The  stem  is  screwed  or  keyed 
into  the  sliding  block  B,  which  is  forked  on 
the  end  so  as  to  provide  a  bearing  for  the 
shaft  of  roller  r.  If  the  camshaft  rotates 
constantly  in  one  direction,  the  center  line 
of  the  camshaft  should  be  set  out  of  line 
with  the  roller  shaft  as  shown  in  the  figure. 
The  direction  in  which  the  shaft  c  should 
be  out  of  line  is  determined  by  the  direc- 
tion of  motion  of  the  camshaft.  The  line 
w  v  should  be  on  the  side  of  x  y  opposite 
the  projection  on  the  cam,  when  the  pro- 
jection is  approaching  the  roller. 

In  laying  out  a  cam,  the  simple  method 
shown  in  Fig.  17  will  give  an  outline  that 
is  suitable  for  nearly  every  condition.  The 
cam  is  made  up  of  two  parts,  a  portion  C 
concentric  to  the  shaft,  and  the  eccentric 
portion  P.  The  part  C  is  usually  turned  a 
little  smaller  than  the  circle  shown  by  the 
dotted  line,  which  is  a  circle  that  would  be 
described  by  the  roller  when  the  valve  is 
down  upon  its  seat  and  all  lost  motion 

73 


79 


is  taken  up  between  the  stem  and  any 
mechanism  which  carries  the  roller.  In 
laying  out  the  eccentric  portion,  it  should 
be  remembered  that  the  valve  does  not 
begin  to  open  until  the  point/,  where  the 
line  m  n  meets  the  dotted  circle,  is  in  con- 
tact with  the  roller.  That  portion  of  the 
revolution  of  the  cam  during  which  the 
valve  is  to  remain  open,  should,  therefore, 
be  laid  off  on  the  dotted  circle  and  not,  as 
the  author  has  seen  it  done,  on  the  concen- 
tric outline  of  the  cam.  The  arc  P  is 
usually  so  laid  out  for  the  exhaust-valve, 
that  it  will  open  the  valve  when  the  piston 
has  completed  about  .9  of  the  working 
stroke  and  close  it  just  as  the  exhaust  stroke 
is  completed.  Hence,  for  the  exhaust  cam 
the  arc  P  should  be  i.i  times  a  quarter  cir- 
cle or  99°,  say  100°  in  round  numbers.  After 
laying  off  100°  on  the  dotted  circle,  draw 
tangents  through  p  and  q  to  the  circular 
outline  of  the  cam,  meeting  it  in  the  points 
m  and/.  Lay  off  the  radial  distance  /  equal 
to  the  movement  of  the  roller  when  it  is 
operating  the  valve,  and  describe  the  arc  n 
k  slightly  rounding  the  corners  at  n  and  k. 
For  the  inlet  cam  the  arc  P  is  usually 
slightly  under  90°  in  order  that  it  may  not 
open  the  inlet  valve  before  the  piston  starts 
on  the  suction  stroke  nor  hold  it  open  after 
the  compression  stroke  has  begun.  The 

80 


bo 

S 


designer  should  exercise  his  judgment  to 
some  extent  in  this  matter,  but  he  will  find 
85°  to  be  very  close  to  the  proper  length  of 
the  arc.  For  the  gas  valve,  a  great  many 
designers  use  the  same  cam  as  for  the  air 
valve.  In  any  case,  the  time  that  the  gas 
valve  should  remain  open  is  practically  the 
same  as  for  the  air  valve,  some  engines  be- 
ing governed  within  limits  by  varying  the 
time  during  which  the  gas  valve  remains 
open. 

An  example  of  a  valve  operating  mechan- 
ism in  which  there  is  no  camshaft,  is  shown 
in  Fig.  18.  In  the  figure,  ^  is  the  exhaust- 
valve  stem.  The  slide  W^  reciprocated  by 
the  eccentric  E  on  the  crankshaft  C,  car- 
ries a  toothed  wheel  X.  To  the  wheel  A' is 
pinned  the  ratchet  wheel  Y  which  has  just 
twice  the  number  of  teeth  that  are  on  A". 
At  each  stroke  of  the  slide  W,  made  in  the 
direction  of  the  crankshaft,  the  pawl  p 
rotates  the  wheels  X  and  Y  so  that  a  tooth 
T  and  a  notch  jVare  presented  alternately 
to  the  stem  s.  Hence  the  valve  is  opened 
but  once  during  two  revolutions  of  the 
engine.  It  is  claimed  by  those  manufactur- 
ers who  employ  this  and  similar  devices, 
that  the  valve  opens  much  more  quickly 
than  with  the  cam,  and  a  better  perform- 
ance of  the  engine  is  obtained  in  conse- 
quence. There  are  several  varieties  of 

82 


valve-motion  dependent  upon  an  eccentric 
and  a  device  similar  to  that  shown  in  Fig. 
18,  nearly  all  of  which  are  the  same  in  prin- 
ciple as  the  device  shown.  A  number  of 
devices  for  avoiding  the  two-to-one  reduc- 
tion have  been  patented,  a  few  of  which  are 
in  use,  but  the  majority  of  the  four-cycle 
engines  are  using  the  camshaft. 

For  transmitting  motion  from  the  crank- 
shaft to  the  camshaft,  there  are  three  kinds 
of  gears  employed— the  ordinary  spur  gear, 
the  bevel  gear  and  the  skew  gear.  The 
spur  gear  is  that  which  has  its  teeth  on  the 
periphery  of  a  disk,  and  is  used  for  trans- 
mitting motion  between  shafts  which  are 
parallel.  It  is  the  most  familiar  of  the 
three.  The  bevel  gear  has  its  teeth  on  the 
surface  of  a  cone  and  is  used  for  transmit- 
ting motion  between  shafts  at  an  angle  but 
which  lie  in  the  same  plane.  The  skew 
gear  is  one  in  which  the  teeth  are  in  the 
form  of  a  screw  thread  or  helix — a  screw 
with  a  multiple  thread — and  is  used  for 
transmitting  motion  between  shafts  which 
are  at  an  angle  and  which  do  not  lie  in  the 
same  plane. 

Examples  of  these  three  varieties  of  gear 

are  shown  in  Fig.  19.     At  (A)  is  shown  a 

pair  of  spur  gears  for  transmitting  motion 

from  the  crankshaft  s  to  the  camshaft  Sf 

.  and  at  the  same  time  reducing  the  velocity  of 

83 


S4 


5  to  half  that  of  s.  The  size  of  pinion  p  is 
made  one-half  that  of  the  gear  <7,  in  order 
to  make  the  proper  reduction  in  speed. 
The  two  shafts  are  parallel.  At  (B)  is  shown 
a  pair  of  bevel  gears  for  changing  the 
direction  of  motion  and  at  the  same  time 
making  the  two-to-one  reduction.  The 
shafts  lie  in  the  same  plane,  that  is  to  say, 
straight  lines,  as  x y,  p  q,  etc.,  may  be  so 
drawn  as  to  pass  through  the  centers  of  the 
two  shafts.  At  ( G)  is  shown  a  pair  of  skew 
gears  in  which  the  speed  reduction  may  be 
made  without  making  the  slower  rotating 
gear  the  larger.  In  fact,  the  gear  on  the 
camshaft  may  be,  and  usually  is  made 
smaller  than  that  on  the  crankshaft.  An- 
other advantage  is  that  the  two  shafts  do 
not  lie  in  the  same  plane.  Motion  may  be 
transmitted  with  these  gears  without  the 
noise  that  is  more  or  less  evident  when  the 
spur  or  the  bevel  gear  is  used. 

Engines,  which  are  fitted  with  spur  gears, 
usually  have  the  camshaft  near  the  crank- 
shaft, and  the  valve-stems  project  from  the 
valve  boxes  in  a  direction  parallel  to  the 
axis  of  the  cylinder.  This  arrangement 
necessitates  either  long  stems  on  the  valves, 
or  a  long  rod  from  the  camshaft  to  the  end 
of  the  valve-stem.  In  some  engines,  this 
feature  is  avoided  by  the  use  of  a  train  of 
spur  gears  which  brings  the  camshaft  close 


to  the  valve  boxes.  In  a  carefully  designed 
engine,  there  is  110  objection  to  the  use  of 
spur  gears,  and  their  use  often  saves  ex- 
pense in  construction. 

Very  few  engines  employ  the  bevel  gear, 
as  it  is  a  somewhat  difficult  matter  to  so 
arrange  them  on  the  engine  that  they  will 
not  take  up  an  undesirable  amount  of  room. 
The  skew  gear  obviates  this  latter  difficulty 
to  a  great  extent,  and  it  allows  the  cam- 
shaft to  be  placed  in  a  position  from  which 
it  is  more  convenient  to  operate  the  valves. 
Either  gear  may  be  used  to  operate  a  cam- 
shaft the  axis  of  which  is  parallel  to  the 
axis  of  the  cylinder,. and  by  the  use  of  the 
second  pair  of  gears  the  shaft  may  be  given 
a  second  quarter  turn  and  run  across  the 
back  of  the  cylinder  head  to  operate  valves 
that  are  placed  in  the  head.  Where  there 
are  two  or  more  cylinders,  it  will  add  to  the 
economy  of  construction,  if  a  single  cam- 
shaft is  employed  to  carry  all  the  cams. 
This  shaft  should  then  be  placed  so  that 
the  axis  is  at  a  right  angle  to  the  axes  of 
the  cylinders. 


86 


CHAPTER  XI. 

GOVERNORS. 

All  gas  engines  are  governed  by  eitlier 
cutting  out  or  cutting  in  impulses  to  the 
piston,  or  by  reducing  or  increasing  the 
force  applied  the  piston  according  to  the 
requirements.  Regulating  the  speed  of  the 
engine  by  varying  the  number  of  impulses 
given  to  the  piston  is  called  the  hit-and-miss 
system.  There  is  no  term  at  present  in  use 
that  will  cover  all  cases  of  governing  by 
varying  the  strength  of  the  impulse,  and 
the  author  suggests  the  term  variable 
impulse.  There  are  three  methods  of  gov- 
erning under  each  of  the  above  two  systems 
of  regulation,  as  described  below. 

HIT-AND-MISS. 

I.  Holding  the  gas  valve  closed  during 
one  or  more  revolutions  of  the  engine  when 
running  below  full  power.  During  the  idle 
strokes  the  engine  is  compressing  and 
expanding  a  charge  of  pure  air. 

87 


II.  Stopping  the  action  of  the  exhaust 
valve,  holding  it  either  open  or  closed  dur- 
ing  the   idle  strokes.     When  the  valve  is 
held  open  there  is  not  sufficient  suction  to 
open  the  inlet  valve,  this  method  usually 
being  employed  on  engines  having  a  suc- 
tion valve.     In  the  latter  case  the  engine 
retains    the    products   of   combustion,  the 
pressure  within  the  cylinder  being  at  all 
times  too  great  to  allow  a  fresh  charge  to 
enter. 

III.  Cutting  off  the   current  from   the 
igniter,    employed,    of    course,    where     an 
electric  igniter  is  used.     The  governor  is, 
in  this  case,  attached  to  a  switch,  which  is 
opened    whenever    the    speed    passes   the 
limit.    In  this  case  the  charge  is  alternately 
compressed  and  expanded  until  the  switch 
is  closed  and  ignition  takes  place. 

A  fourth  method  might  be  added  to  this 
class,  i.  e.,  the  stopping  of  the  camshaft. 
With  this  method  all  operations  are  halted, 
usually  with  the  exhaust  valve  held  open. 

VARIABLE    IMPULSE. 

IV.  Partial  stoppage  of  the  gas  supply. 
The   mixture   of    fuel   and   air   retains    its 
explosive  properties  within  certain  limits  of 
the   proportion   between    the   two.     If  the 
mixture  is  poor  in  gas  the  impulse  is  cor- 
respondingly weakened,  and  up  to  the  point 

88 


whereat  the  charge  explodes  with  the 
greatest  force,  the  strength  of  the  impulse 
may  be  increased.  There  is  also  a  lower 
limit,  beyond  which  the  mixture  becomes 
so  poor  in  gas  that  it  will  not  explode. 
After  passing  this  limit  it  is  necessary  to 
resort  to  the  hit-and-miss  method  I,  and 
cut  out  the  gas  supply  entirely.  '» 

V.  Throttling  the  charge.    This  method 
reduces    the   strength   of    the   impulse    by 
reducing  the  quantity  of  the  charge   that 
enters  the  cylinder,  the  proportions  of  fuel 
and  air  remaining  the  same  at  all  times. 

VI.  Varying  the  point  of  ignition.     The 
greatest '  mean  effective  pressure   in   a  gas 
engine   is   obtained   when    the    spark    has 
sufficient  lead  to  bring  the  maximum  pres- 
sure at  the  beginning  of  the  stroke.     If  the 
lead  is  reduced,  or  made  negative  (ignition 
delayed   until   the   crank    has    passed    the 
center),  the  strength  of  the  impulse  may 
be  varied. 

Hit-and-miss  regulation  is  that  which 
gives  the  greatest  economy  of  fuel  con- 
sumption. There  is  little  choice  between 
the  three  methods  given  above,  as  all  have 
advantages  and  disadvantages  that  make 
them  about  equally  good. 

Of  the  variable  impulse  methods,  No.  IV 
is  that  which  gives  the  best  fuel  economy, 
the  compression  is  the  same  at  every 


cycle.  The  objection  to  this  plan  is,  the 
return  to  the  hit-and-miss  system  as 
soon  as  the  speed  falls  to  the  limit  below 
which  the  charge  would  be  too  poor  in  gas 
to  explode.  Method  V  has  been  used  quite 
successfully  for  engines  driving  dynamos, 
but  it  does  not  give  the  economy  that  is 
derived  from  an  engine  employing  one  of 
the  first  four  methods.  The  method  de- 
scribed last,  is  perhaps  the  most  wasteful  of 
fuel  after  the  lead  is  late  enough  to  form  a 
perceptible  reduction  in  the  area  of  the 
indicator  diagram.  The  result  obtained  is 
shown  very  plainly  in  the  chapter  on  indi- 
cator diagrams.  This  method  of  speed 
regulation  is  of  little  service  where  econ- 
omy is  desired,  but  where  economy  is  a 
secondary  consideration,  as  in  an  automo- 
bile engine,  it  is  a  very  simple  method  of 
governing. 

Governors  of  three  different  kinds  are 
employed  on  gas  engines.  Two  of  these 
are  of  the  centrifugal  type,  similar  to  the 
governors  in  use  on  the  steam  engine,  the 
other  is  a  governor  made  possible  by  the 
hit-and-miss  system  of  regulation  and  is 
known  as  the  pendulum  or  inertia  governor. 
The  centrifugal  governors  are  the  conical 
pendulum  and  the  shaft  governor.  Hither 
of  these  two  may  be  employed  for  any 
method  of  regulation  while  the  pendulum 

90 


governor  may  he  used  only  for  the  hit-and- 
miss. 

An  example  of  the  conical  pendulum  gov- 
ernor is  shown  in  Fig.  20  as  arranged  to 
operate  a  throttling  device.  The  two  balls 
bb  are  rotated  from  the  camshaft,  or  other 
convenient  revolving  portion  of  the  engine, 
through  the  bevel  gears  pq.  As  the  speed 
of  rotation  increases,  the  balls  move  in  the 
direction  of  the  arrows,  compressing  the 
spring  s  and  depressing  the  stem  »S  of  the 
valve  Fby  means  of  the  collars.  As  the 
valve  moves  downward,  the  holes  a  and  g 
are  gradually  covered  by  the  wall  of  the 
passage,  contracting  the  opening  from  the 
gas  passage  G  and  the  air  passage  A  into 
the  chamber  X,  and  preventing  the  mixture 
from  flowing  in  as  great  a  quantity  as  before, 
into  the  inlet  port  /. 

An  example  of  the  shaft  governor  is 
shown  in  Fig.  21,  in  connection  with  a  de- 
vice for  opening  the  gas  valve  only  when 
the  engine  is  below  speed.  The  balls  bb  are 
on  the  end  of  the  short  arms  //  pivoted  at  pp. 
As  the  crankshaft  C  revolves,  the  balls  tend 
to  swing  in  the  direction  indicated  by  the 
arrows,  but  they  are  withheld  by  the  springs 
s.  As  the  balls  swing  about  the  pivots  />/>, 
the  opposite  ends  of  the  arms  //  move  toward 
X  and  carry  with  them  the  collar  c.  A 
long  lever  m  with  a  fulcrum  pivot  at  P  is 

92 


93 


carried  with  the  collar  and  the  long  end 
pushes  the  point  out  of  line  with  the  stem 
v  of  the  gas  valve.  The  point  x  is  attached 
to  the  air  valve  mechanism  so  that  it  rocks 
backwards  and  forwards  at  every  movement 
of  the  air  valve.  When  the  speed  is  too 
high  the  governor  causes  the  point  x  to 
miss  the  valve-stem  and  no  gas  enters  the 
cylinder. 

In  Fig.  22  is  illustrated  one  form  of  the 
pendulum  or  inertia  governor  arranged  to 
hold  the  exhaust  valve  open  so  long  as  the 
engine  is  above  speed.  The  valve  stem  is 
operated  from  the  camshaft  by  means  of 
the  slide  M.  On  the  slide  is  carried  the 
pendulum  P  which  swings  about  the  pivot 
J>.  If,  upon  the  return  of  the  slide,  the 
speed  is  higher  than  that  for  which  the 
governor  is  set,  the  pendulum  lags  behind 
and  the  end  of  the  long  arm  a  of  the  bell- 
crank  to  which  the  pendulum  is  attached, 
strikes  the  pin  c  and  throws  it  in  the  path 
of  the  block  B,  holding  the  valve  open. 
Upon  the  following  stroke  of  the  slide,  the 
valve-stem  >S  receives  a  thrust  sufficiently 
long  to  allow  the  pin  c  to  drop  out  of  the 
way  of  B  unless  the  arm  a  is  still  in  the 
way.  If  the  arm  allows  the  pin  to  drop,  the 
valve  closes  and  the  engine  takes  up  its 
cycle  once  more.  The  speed  of  the  engine 
may  be  varied  by  a  simple  adjustment  of 

94 


b 

s 


95 


the  pendulum  ball  P.  If  it  is  desired  to 
increase  the  speed  of  the  engine,  the  set 
screw  n  is  loosened  and  the  ball  P  is  raised. 
L/owering  the  pendulum  makes  the  gov- 
erner  act  at  a  lesser  speed. 

This  form  of  governor  is  also  much  used 
to  control  the  gas  valve.  The  long  arm  a 
of  the  bell-crank  is  pointed  and  it  is  used 
to  give  the  necessary  thrust  to  open  the 
valve.  In  case  the  speed  rises  above  a  cer- 
tain amount  the  arm  a  swings  aside  and 
misses  the  gas  valve  stem. 


96 


CHAPTER  XII. 

STARTERS. 

Engines  larger  than  eight  or  ten  horse- 
power are  difficult  to  start  by  turning  the 
flywheel  by  hand,  and,  in  order  to  lessen 
the  amount  of  labor  involved,  larger  en- 
gines than  the  above  are  usually  supplied 
with  some  device  by  means  of  which  an 
impulse  may  be  given  to  the  piston  when 
the  engine  is  at  rest,  that  will  be  strong 
enough  to  propel  the  engine  for  three  or 
more  revolutions  and  until  it  can  take  up 
its  cycle  and  receive  an  impulse  in  the 
regular  way.  The  methods  in  use  for  this 
purpose  are  so  numerous  that  but  a  few 
examples  may  be  illustrated  in  a  volume  of 
this  nature. 

The  first  method  to  suggest  itself  to  an 
engineer  would  obviously  be  to  apply  pres- 
sure to  the  engine  for  one  or  more  strokes- 
from  an  exterior  source,  as  from  a  steam 
boiler  or  from  a  tank  of  compressed  air.  In 
fact,  the  compressed  air  starter  is  a  most 

97 


convenient  form.  It  is  very  simple  and 
-consists  of  a  small  air  pump  and  a  storage 
lank  for  the  air.  A  pipe  connects  the  tank 
to  the  cylinder  of  the  engine,  and  this  pipe 
is  supplied  with  a  two-way  plug-valve.  The 
lank  is  filled  with  air,  at  a  pressure  of  forty 
pounds  or  over^when  the  engine  is  running, 
the  pump  being  operated  by  means  of  a 
belt  from  the  line  shaft  or  other  convenient 
point.  When  it  is  desired  to  start  the  en- 
gine the  flywheel  is  turned  until  the  cam- 
shaft is  in  the  proper  position  for  the 
•exhaust  stroke,  and  until  the  crank-pin  is 
just  above  the  back-center.  The  air-valve 
is  then  opened  wide,  and  closed  again  as 
soon  as  the  piston  nears  the  end  of  its 
stroke.  If  the  impulse  is  not  strong  enough 
to  give  the  engine  a  sufficient  start  it 
should  be  repeated  at  the  next  revolution 
l)ut  one.  Two  impulses  with  the  air  are 
usually  more  than  enough  for  the  purpose. 
After  the  engine  is  under  way,  the  fuel 
should  be  turned  011  as  directed  in  the 
chapter  on  Starting.  If  the  engine  has 
more  than  one  cylinder,  one  cylinder  may 
be  used  to  start  while  the  remaining  cylin- 
ders are  taking  up  the  cycle.  Occasionally, 
the  engine  is  fitted  with  a  special  valve 
mechanism,  for  the  purpose  of  starting  with 
•compressed  air,  so  arranged  that  an  impulse 
is  given  to  the  piston  by  the  air  at  every 

9s 


Fig.  23. 


99 


revolution  until  the  speed  is  sufficient  to 
lake  up  the  cycle. 

A  class  of  starters  that  is  very  much  in 
use  on  engines  of  fifty  horsepower  and 
l>elow,  is  simply  a  means  of  igniting  a 
charge  that  has  been  drawn  into  the  engine 
by  turning  it  over  by  hand.  For  instance, 
a  certain  manufacturer  equipped  his  engines 
with  what  is  called  a  match  igniter.  This 
igniter  is  shown  in  section  in  Fig.  23.  The 
igniter  consists  of  the  casting  B  which  is 
screwed  into  an  opening  into  the  valve-box. 
It  contains  a  plunger  consisting  of  a  tapered 
and  roughened  head  A,  a  stem  d  and  a  cap 
C.  The  plunger  is  held  at  the  top  of  its 
stroke  by  means  of  the  spring  S.  A  small 
pet  cock  s  is  screwed  into  the  side  of  B, 
through  which  is  inserted  a  parlor-match  m, 
the  plug  h  is  then  turned  so  as  to  break  the 
match-stick  and  hold  it  in  place.  When 
the  engine  is  under  way  the  cock  s  is  opened 
and  the  burnt  match  expelled  by  the  next 
explosion  within  the  engine. 

To  start  the  engine,  it  is  turned  over  until 
the  igniter  snaps,  and  a  charge  of  air  is 
drawn  in  by  turning  the  flywheel.  At  the 
same  time,  a  small  quantity  of  gasoline — 
the  amount  depending  upon  the  size  of  the 
engine — is  drawn  in  with  the  air.  The  en- 
gine is  now  turned  over  until  the  piston  is 
at  nearly  the  end  of  the  stroke  ;  the  engine 


is  then  reversed  compressing  fh^  ciii.r^e 
by  a  quick  backward  turn  of  the  flywheel, 
the  cap  C  of  the  igniter  is  struck  with  the 
hand  lighting  the  match  m  and  firing  the 
charge.  The  explosion  is  usually  of  suffi- 
cient force  to  turn  the  engine  until  it  can 
take  up  its  cycle. 

In  some  engines,  the  use  of  the  match 
igniter  is  avoided  by  means  of  a  device 
which  operates  the  electric-igniter  at  the 
proper  moment.  When  the  jump-spark  is 
employed,  a  switch  which  will  close  the 
primary  circuit,  is  all  that  is  necessary.  In  j 
other  engines  the  flywheel  is  turned  until 
the  camshaft  is  at  the  proper  position  for 
the  beginning  of  the  suction  stroke,  and 
the  crank-pin  is  on  the  inner  center.  A 
charge  of  fuel  and  air  is  then  pumped  into 
the  cylinder  by  hand.  The  pressure  within 
the  cylinder  can  be  determined  by  the  force 
necessary  to  work  the  pump  or  by  setting 
the  engine  a  little  past  the  center  and  hold- 
ing the  flywheel,  noting  when  it  begins  to 
pull.  When  the  required  pressure  is  ob- 
tained, the  flywheel  should  be  turned  until 
the  pin  is  about  10°  past  the  center  and  the 
charge  fired  by  means  of  a  match  igniter  or 
equivalent  device. 

In  large  engines,  where  the  horsepower 
is  100  h.  p.  or  above,  a  small  gas  engine, 
which  may  be  easily  started  bv  hand,  is 


.  employed  to'  Inrn  t#e  large  engine  over 
until  it  takes  up  its  cycle,  and  the  starting 
engine  is  then  uncoupled  automatically. 
Sometimes  the  valve  mechanism  of  the  en- 
gine is  so  arranged  that,  after  the  engine  is 
uncoupled  from  the  line  shaft  and  before  it 
is  stopped,  it  is  employed  to  charge  a  pres- 
sure tank  by  permitting  a  portion  of  the 
expanding  charge  to  pass  into  the  tank. 
This  is  accomplished  by  opening  communi- 
cation with  the  tank  after  the  piston  has 
made  a  portion  of  its  expansion  stroke,  the 
first  portion  of  the  stroke  being  used  to 
impart  motion  to  the  engine. 


CHAPTER  XIII. 

ENGINES   FOR   AUTOMOBILES. 

The  requirements  of  an  automobile  en- 
gine are  lightness,  compactness,  minimum 
vibration,  wide  range  of  speed  under  con- 
trol of  the  operator,  and  simplicity.  Econ- 
omy of  fuel  consumption  is  a  secondary 
consideration.  The  fewer  the  cams,  levers, 
etc.,  on  an  automobile  engine,  the  less  liable 
will  it  be  to  get  out  of  order.  It  was  for- 
merly supposed  by  the  gas-engine  builder 
that  a  gas  engine  must  run  at  a  constant 
speed,  and  all  changes  of  speed  made  by 
means  of  gears.  Recent  experiments  have 
exploded  this  theory  and  successful  engines 
are  now  on  the  market  which  will  run  at 
speeds  varying  from  100  to  1000  r.  p.  m.  for 
the  same  engine.  At  least  one  manufacturer 
claims  that  his  engine  may  be  run  at  speeds 
ranging  from  100  to  2000  r.  p.  m.  Two- 
methods  are  employed  for  governing  the 
speed  of  the  engine.  One  is  by  throttling 
the  charge,  and  the  other  by  changing  the 

103- 


lead  of  the  spark.  Hither  of  these  methods 
gives  an  impulse  at  each  cycle.  Bngines 
operating  on  the  hit-and-miss  principle,  are 
useless  for  motor  vehicles. 

For  single-seated  carriages,  an  engine 
capable  of  giving  at  least  four  horsepower 
at  between  500  and  600  r.  p.  m.  should  be 
employed.  If  the  carriage  is  likely  to  be 
•called  upon  for  heavy  hill-climbing  or  rac- 
ing speeds  the  horsepower  should  be  in- 
creased to  six.  For  motor  bicycles  one 
liorsepower  is  usually  sufficient,  while  for 
tricycles  two  horsepower  is  that  generally 
employed.  Single-cylinder  engines  will  not 
run  in  a  horizontal  position  without  caus- 
ing an  annoying  amount  of  vibration  to  be 
transmitted  to  the  vehicle.  If  it  is  desired 
to  use  a  single-cylinder  engine  it  should  be 
placed  with  the  cylinder  vertical  and  the 
engine  very  carefully  balanced.  Two-cylin- 
der engines  with  the  cylinders  placed  end 
to  end,  each  connecting-rod  being  attached 
to  a  separate  crank-pin  and  the  crank-pins 
placed  180°  apart,  will,  if  all  parts  are  care- 
fully made  of  the  same  weight,  run  with 
,  very  little  vibration.  The  reciprocating  and 
rotating  parts  of  the  two  engines  balance 
each  other.  Two  cylinders  with  their  axes 
parallel  and  the  open  ends  in  the  same 
direction,  work  very  well  when  the  cranks 
are  set  at  180°,  but  still  better  results  in 

104 


the  matter  of  balancing  are  obtained  by 
the  use  of  three  or  four  cylinders  with  the 
cranks  equally  spaced  about  the  crank- 
circle. 

Among  the  automobile  builders,  the  jump- 
spark  is  finding  favor,  as  it  may  be  better 
controlled  at  the  high  rotative  speeds  at 
which  these  engines  run.  The  change  of 
lead  for  the  spark  may  be  obtained  by  rotat- 
ing the  cam  or  switch,  as  the  case  may  be, 
around  the  camshaft.  Governors  for  auto- 
mobile engines  are  very  well  in  theory,  to 
prevent  the  engine  from  speeding  up  when 
an  obstruction  throws  one  of  the  wheels  off 
the  ground,  but  there  is  no  governor  writhin 
the  knowledge  of  the  writer  that  will  act 
within  a  time  sufficiently  short  for  the  pur- 
pose. The  speed  of  the  engine  should 
always  be  at  the  control  of  the  operator.  If 
the  engine  speed  is  under  control,  there 
will  be  but  two  changes  of  speed  required, 
one  for  levels  and  easy  grades  and  the  other 
for  hill-climbing.  The  reversing  gear  may 
be  connected  to  the  hill-climber  as  a  high 
speed  is  undesirable  for  going  backward. 

For  cooling  the  cylinders,  both  a  closed 
circulating  water  system  is  employed,  and 
also  ribs  radiating  from  the  cylinder-walls. 
The  latter  may  not  be  used  successfully  on 
cylinders  over  3^  to  4  inches  diameter. 
For  an  engine  employing  a  water-jacket 

105 


there  should  be  some  method  of  cooling 
the  water,  otherwise  the  amount  of  water 
which  it  is  necessary  to  carry  becomes 
excessive.  In  France,  where  the  gasoline 
automobile  is  in  extensive  use,  a  coil  of 
pipe  with  collars  to  increase  the  radiating 
surface  of  the  pipe  is  considerably  employed. 
These  collars  or  disks  are  stamped  from 
sheet  metal  and  punched  with  a  star-shaped 
hole  in  the  center  and  then  forced  over  the 
tube,  while  the  tube  is  straight.  Afterward 
the  tube  is  coiled  on  a  comparatively  small 
radius.  This  coil  is  made  a  part  of  the 
circulating  system  and  answers  its  purpose 
very  effectively.  The  author  would  suggest 
that  if  means  were  taken  to  guide  air 
through  these  coils  by  means  of  a  curved 
shield  under  the  carriage  it  would  increase 
the  cooling  efficiency  of  the  coil. 

The  gasoline  and  the  water-tanks  should 
each  have  some  means  by  which  the  quan- 
tity of  the  liquid  contained  in  them  could 
be  determined  at  any  time  without  it  being 
necessary  for  the  operator  to  leave  his  seat. 
All  parts  of  the  mechanism  should  be  com- 
pletely enclosed  to  protect  them  from  dust. 
For  this  reason  an  enclosed  crank-chamber 
is  a  desirable  feature.  Lubrication  of  every 
part  should  be  strictly  automatic,  so  that 
when  the  carriage  has  been  given  the 
proper  attention  at  the  outset  of  a  trip  it 

106 


will  need  no  further  attention  for  a  reason- 
able time  at  least.  The  fuel  feed  should  be 
so  regulated  that  110  odor  of  consequence 
is  noticeable  at  the  exhaust  opening.  The 
fuel  should  be  under  control  in  order  that 
it  may  shut  off  when  going  down  grade,  or 
when  stopping  the  engine.  The  exhaust- 
muffler  should  be  a  good  one,  as  excessive 
noise  is  an  objectionable  feature.  It  is  nec- 
essary to  sacrifice  a  little  power  to  get  good 
results  with  the  muffler,  but,  as  already 
noted,  the  fuel  economy  is  a  secondary 
consideration. 


107 


CHAPTER  XIV. 

GAS-KNGINE     DIAGRAMS. 

It  is  quite  a  general  custom,  among  the 
manufacturers  of  gas  engines,  to  base  the 
rated  horsepower  of  an  engine  upon  its  per- 
formance with  natural  gas  of  an  average 
quality.  If,  therefore,  a  diagram  may  be 
laid  out  which  will  show  the  conditions 
within  the  engine  cylinder  during  the  cycle, 
when  working  under  average  conditions,  it 
will  prove  of  valuable  assistance  to  the 
designer.  In  order  that  the  reader  may 
know  what  to  expect,  when  about  to  con- 
sider a  departure  from  the  practice  of  the 
present  builders  writh  reference  to  compres- 
sion, and  also  that  he  may  have  an  ideal  dia- 
gram with  which  to  compare  those  he  may 
obtain  from  the  engine  after  it  is  built,  the 
author  will  show  just  how  such  a  diagram 
may  be  built  up  by  the  aid  of  formulas. 

An  ideal  diagram  for  an  engine  working 
with  natural  gas  as  a  fuel,  is  shown  in  Fig. 
24.  Before  laying  out  the  diagram  it  is 

108 


necessary  to  decide  upon,  either  the  com- 
pression pressure  desired,  or  upon  the  ratio 
of  the  volume  of  the  compression  space  to 
that  displaced  by  the  piston  during  the 
stroke.  For  the  diagram  in  the  figure,  the 
ratio  has  been  taken  as  30  percent.  The 
total  volume  of  the  cylinder,  when  the  pis- 
ton is  at  the  end  of  its  outward  stroke,  is 
therefore  i  -f-  .3  =  1.3  of  the  piston  displace- 
ment. As  it  is  much  more  convenient  to 
consider  the  total  cylinder  volume  as  unity 
for  the  purpose  of  making  the  calculations, 
it  is  necessary  to  find  what  proportion  of  the 
total  cylinder  volume  is  included  in  the 
compression  space,  or  to  divide  .3  by  1.3, 
giving  .2308  as  this  ratio.  In  calculating 
the  pressures  at  various  points  upon  the 
curves,  the  following  formulas  should  be 
used,  because  they  represent  the  average 
behavior  of  the  gases  shown  by  actual 
indicator  diagrams  taken  from  engines  in 
operation.  For  the  compression  curve 

PV-*=K      (i) 

Wherein  P=  the  pressure   above   a  vacu- 
um or  absolute  pressure ; 

V=  the  volume  of  the  gases  at 
the  time  they  are  at  the  pressure  P; 

K  =  a  number  or  constant  de- 
pending upon  the  conditions,  but  which 
is  the  same  for  all  parts  of  the  same 
curve. 


When  the  volume  of  the  cylinder  is  con- 
sidered as  unity,  A"  becomes  the  absolute 
pressure  of  the  atmosphere,  usually  taken 
as  14.7.  When  natural  gas  is  employed  at 
the  proportion  to  air  which  gives  the  best 
effect,  the  pressure  of  the  gases  after  explo- 
sion is  four  times  the  pressure  after  com- 
pression, both  these  pressures  being  those 
above  the  atmosphere. 

The  formula  for  the  expansion  curve  is 

/>F'-35=   C   (2) 

Wherein  P  and  V  have  the  same  signifi- 
cance as  in  formula  (i)  and  C  is  a  constant 
depending  upon  the  maximum  pressure. 

These  equations  may  also  be  written  as 
follows  : 

Py*-3=PV*.3t  />^i.35=JpK«.3S> 

a  form  which  shows  the  exact  relation  be- 
tween any  two  points  on  the  curve. 

In  order  that  the  reader  may  better  see 
how  to  apply  the  above  formulas,  the  com- 
putation of  the  diagram  in  Fig.  24  will  be 
given.  Taking  first  the  computation  of  the 
pressure  at  the  end  of  the  compression 
stroke,  and  applying  formula  (i) 

/>K'.3  =  ^=i4.7,  and  P=m     = 


In  order  to  find  the  denominator  of  this 
fraction,  it  is  necessary  to  multiply  the  true 


logarithm  of  the  number  by  1.3.  The  log- 
arithm of  .2308  as  found  in  a  table  of  log- 
arithms (the  tabular  logarithm)  is  1.363236, 
and  since  the  logarithm  has  a  negative 
characteristic  (number  to  left  of  decimal 
point),  the  true  logarithm  must  be  found 
by  adding  the  mantissa  (number  to  right  of 
decimal  point)  to  the  characteristic  as 
follows : 

i. oooooo 
•363236 
.636764 


1910292 
636764 

^.8277932 

1.172207  (subtracting  from  i  and  add- 
ing —  T  to  get  the  tabular  log) . 

Log  14.7=1.167317,  and  subtracting  the 
log  of  (.23O8)1-3  the  resulting  log  is  that  of 
the  compression  pressure  at  the  end  of  the 
stroke. 

£•167317 

1.172207 

1.995110  =  log  of  98.88.  98.88  Ib.  is 
the  compression  pressure  in  Ib.  per  sq.  in. 
above  a  vacuum.  For  practical  purposes, 
three  figures  will  be  sufficient  and  98.9  may 
be  taken  as  the  pressure.  The  pressure 
above  the  atmosphere  would  be  98.9 — 14.7 
--=  84.2  Ib.  per  sq.  in.  To  get  the  maximum 


pressure,  this  amount  should  be  multiplied 
by  4,  giving  84.2  X  4^=336-8  lb->  and  336-8  -f 
14.7  —  351.5  lb.  absolute  pressure. 

In  order  that  the  proper  shape  of  the 
curve  may  be  very  closely  approximated,  it  is 
best  to  compute  the  pressures  at  three  points 
between  the  ends.  The  points  for  which 
the  calculations  in  the  figure  were  made 
are  those  when  the  volumes  are  .35,  .5  and 
.75,  and  in  case  of  any  uncertainty  a  point 
should  be  taken  midway  between  .35  and 
the  higher  end  of  the  curve.  The  pressures 
corresponding  to  the  points  given,  are  57.6, 
36.2  and  21.4  respectively. 

The  pressures  for  the  expansion  curve 
are  found  in  the  same  manner  as  for  the 
compression  curve,  but  by  means  of  formula 
(2).  Before  this  formula  is  applied,  how- 
ever, it  is  necessary  to  find  the  value  of 
the  constant  C,  which  is  the  pressure  at  the 
end  of  the  stroke  when  the  volume  is  equal 
to  i.  Hence  PI'1**  —  C  becomes  351.5  X 

(.23o8)I-35  =  C. 

Log     (,23o8)I-35  ==   1.140368,  Log  351.5  = 
2.545925.     Adding  these  logs  gives,  for  the 
sum,  the  log  of  the  constant  C,  thus : 

1.140368 

2.545925 

1.686293  =  lo£  48-56-  48-56  lbs.  is  the 
terminal  pressure  of  the  gases  in  the  cylin- 
der, should  release  take  place  at  the  end  of 


the  stroke.  Hence  the  equation  of  the 
expansion  curve  is  PV*  *&  =  48.56. 

The  intermediate  pressures  for  the  rer 
mainder  of  the  expansion  curve  are  found 
by  subtracting  the  logs  of  .35,  .5  and  .75 
raised  to  the  1.35  power,  from  the  log  of 
48.56.  They  are  200.4,  I23-8  and  71.6  respec- 
tively. After  these  points  are  located,  the> 
diagram  is  constructed  by  drawing  the 
curves  through  them  as  shown  in  the  fig- 
ure. The  length  of  the  diagram  is  3^'' 
from  the  line  D  C  to  £,  and  the  scale  of  the 
spring  represented  is  160  Ib.  Hence  unit 
volume  is  represented  by  a  length  of  3%//, 
and  a  height  of  one  inch  on  the  diagram 
represents  a  pressure  of  160  Ibs.  per  sq.  in. 

In  order  to  make  the  diagram  complete, 
it  is  necessary  to  add  the  two  small  curves 
.at  i  and  r  e.  The  curve  at  i  is  that  due  to 
the  lead  of  the  ignition  which  causes  an  in- 
crease of  the  rate  at  which  the  pressure  is 
rising.  It  can  be  drawn  but  approximately, 
as  it  varies  in  size  for  any  change  in  the 
piston  speed.  Its  effect  upon  the  area  of 
the  diagram  is  too  small  to  be  of  conse- 
quence, and  the  only  value  it  has,  is  to  serve 
as  a  memorandum  when  using  the  diagram 
for  the  purpose  of  comparison  with  those 
actually  taken  from  the  engine.  The  curve 
r  c  is  that  produced  by  the  release  taking 
place  before  the  end  of  the  stroke  is  reached. 

114 


The  point  of  release  r  should  be  such  as  to 
bring  the  point  e  where  the  expansion  line 
meets  the  atmospheric  line  A  B  at  the  end 
of  the  stroke.  To  draw  this  curve  as  it  is 
shown  in  the  figure,  erect  the  vertical  line 
j?  r  at  a  distance  from  Xm  equal  to  .9  time 
the  length  of  the  diagram,  which,  in  the 
figure,  is  .9  X  -77— -693  time  the  unit  length. 
Through  r  and  c  describe  a  circular  arc, 
which  shall  be  tangent  to  the  expansion 
line  at  r.  Joining  the  points  i  and  m  with 
a  straight  line  completes  the  diagram. 

The  diagram  having  been  drawn,  the  de- 
signer may  find  the  M.  E.  P.  by  means  of 
planimeter  as  explained  in  the  chapter  on 
Testing.  From  the  M.  E.  P.  obtained  from 
this  diagram,  he  may  calculate  the  horse- 
power of  an  engine  of  any  size  which  it  is 
proposed  to  build,  or  he  may  determine  the 
dimensions  of  the  engine.  The  design  of 
the  valve  motions  may,  to  a  certain  extent, 
be  founded  upon  the  diagram,  as  it  shows 
the  proper  time  for  opening  and  closing  the 
valves.  It  should  be  the  aim  of  the  designer 
to  build  an  engine  that  will  give  as  nearly 
as  possible,  such  a  diagram  as  that  shown 
in  the  figure,  for  only  with  a  diagram  of  this 
shape  are  the  best  results  obtained. 

A  few  diagrams  will  now  be  shown  which 
have  been  made  by  an  engine  when  not 
working  under  the  conditions  necessary  for 


producing  a  diagram  similar  to  that  in  Fig. 
24.  In  Fig.  25  are  shown  diagrams  taken 
from  various  engines  while  in  actual  opera- 
tion and  they  illustrate  just  what  occurs 
under  several  conditions.  At  (A)  is  shown 
a  diagram  taken  from  an  engine  which  is 
operating  with  everything  in  good  working 
order  with  the  exception  of  an  exhaust  re- 
lease which  is  a  trifle  late,  indicated  by  the 
expansion  line  not  reaching  the  atmpspheric 
line  X  Y  until  the  piston  has  returned  to 
d.  The  point  of  release  is  shown  by  the 
sudden  change  in  the  curvature  of  the  ex- 
pansion line  at  £,  the  point  of  ignition  by 
the  sudden  change  of  curvature  in  the  com- 
pression curve  at  i. 

On  either  side  of  the  atmospheric  line  is 
a  curve  which  is  exaggerated  in  the  draw- 
ing in  order  that  it  may  be  distinct.  The 
upper  curve  is  that  produced  by  pressure 
within  the  engine  cylinder  on  the  exhaust 
stroke,  and  is  due  to  an  unnecessarily  con- 
tracted exhaust  passage,  or  to  obstructions 
that  have  accumulated  in  the  exhaust-pipe. 
The  lower  curve  is  caused  by  the  pressure 
within  the  cylinder  falling  below  that  of  the 
atmosphere,  forming  a  partial  vacuum  be- 
cause of  an  obstructed  inlet  passage.  Ordi- 
narily, these  curves  are  too  small  to  be  of 
any  moment,  but  in  case  they  are  a  quite 
distinct  departure  from  the  atmospheric 

117 


line,  they  show  that  an  unnecessary  amount 
of  work  is  being  done  by  the  piston  in 
forcing  the  gases  through  the  passage,  and 
steps  should  be  taken  to  remedy  the  defect. 
A  condition  of  this  kind  is  spoken  of  as 
wire-drawing.  Diagram  (B)  is  that  produced 
when  the  ignition  of  the  charge  is  late.  In 
this  case  ignition  takes  place  at  i  after  the 
crank  has  passed  the  center.  The  loss  in 
area  of  the  diagram  is  quite  noticeable  when 
comparing  (B)  with  (A). 

The  reader  should  learn  to  distinguish 
between  a  diagram  produced  by  late  igni- 
tion and  that  produced  by  a  weak  or  a 
throttled  mixture.  In  (B)  the  curve  indi- 
cating rise  of  pressure  immediately  after 
ignition,  is  concave,  while  in  (D)  and  (E), 
which  are  diagrams  produced  by  a  wreak 
mixture,  this  curve  is  either  a  straight  line 
or  is  convex.  (G)  is  a  diagram  in  which  the 
ignition  is  very  tardy,  and  the  area  lost  be- 
cause of  late  ignition  is  shown  by  the  dotted 
lines.  Premature  ignition  is  shown  by  (C). 

,  In  this  diagram  the  ignition  is  at  /  and  the 
loss  of  area  is  illustrated  by  the  proper 

'  diagram  being  shown  in  dotted  lines.*  Dia- 
gram (F)  is  an  example  of  the  effect  of  late 
release  together  .with  obstructed  exhaust 
passages. 

When  an  engine  is  operating  on  fuel 
which  ignites  at  a  low  temperature,  as  is 

118 


the  case  with  gasoline  and  acetylene,  the 
propagation  of  the  flame  throughout  the 
mixture  is  very  rapid,  causing  an  explosion 
which  is  almost  instantaneous.  An  example 
of  the  sort  of  diagram  usually  obtained 
with  these  fuels  is  shown  in  Fig.  26.  The 
sudden  blow  given  to  the  piston  of  the 
indicator,  sets  the  spring  in  vibration  and 
produces  the  wavy  line  which  appears  at 
the  point  immediately  following  maximum 
pressure.  This  effect  has  been  attributed 
to  various  causes,  such  as  a  rapid  succession 
of  explosions,  and  these  in  turn  have  been 
said  to  be  caused  by  an  uneven  distribution 
of  the  fuel  within  the  air  (a  stratified 
charge).  The  author  believes  that  very  few 
of  these  curves  are  of  such  a  nature  as  to 
justify  such  a  reasoning.  They  are  all  of 
the  nature  of  a  sine  curve,  the  waves  grad- 
vially  lessening  in  height  as  the  piston 
proceeds  on  its  stroke.  In  using  these 
fuels,  it  is  best  to  make  the  lead  of  the 
igniter  somewhat  less  than  when  using 
natural  gas  or  manufactured  gas.  By  lead  is 
meant  the  time  or  the  distance  before  the 
end  of  the  stroke,  that  ignition  takes  place. 


CHAPTER  XV. 

GAS-ENGINp;    DIMENSIONS. 

The  power  of  any  engine  is  dependent 
upon  four  factors,  the  average  or  mean 
effective  pressure  upon  the  piston  during 
the  stroke,  the  area  of  the  piston  upon 
which  this  pressure  is  exerted,  the  length 
of  the  stroke,  and  the  number  of  times  per 
minute  the  pressure  is  exerted.  The  power 
of  an  engine  computed  from  the  above  fac- 
tors is  known  as  the  indicated  horsepower 
(I.  H.  P.).  The  power  delivered  at  the  pul- 
ley or  obtained  from  the  engine,  and  which 
is  available  for  power  purposes,  is  called  the 
delivered  horsepower  (D.  H.P.)  or  the  brake 
horsepower  (B.  H.  P.)  and  by  some  writers 
the  effective  horsepower  (E.  H.  P.).  The 
use  of  the  latter  abbreviation  is,  however, 
likely  to  cause  confusion  as  the  same  abbre- 
viation is  employed  for  electrical  horse- 
power. The  tef\n  brake  horsepower  is  de- 
rived from  the  manner  of  testing  the  output 


of  the  engine,  which  is  usually  with  some 
form  of  brake.  The  D.  H.  P.  is  the  I.  H.  P. 
minus  the  power  absorbed  in  the  friction 
of  the  engine,  the  latter  being  called  the 
friction  load.  The  ratio  of  the  D.  H.  P.  to 
the  I.  H.  P.  is  called  the  mechanical  effi- 
ciency of  the  engine,  sometimes  abbreviated 

to  M.  E.,  and  M.  B.  =  D'  H'  ^' ,    this    ratio 

being  usually  expressed  in  percent.  Thus, 
if  the  I.  H.  P.  of  an  engine  is  10  H.  P.  and 
the  D.  H.  P.  is  8  H.  P.,  the  M.  E.  =  T8o  =  80 
percent,  and  the  friction  load  =  10  —  8  =  2 
horsepower. 

The  mean  effective  pressure  (M.  E.  P.)  in 
a  gas-engine  cylinder  varies  with  the  fuel, 
the  pressure  after  compression,  the  propor- 
tion of  the  mixture  and  the  time  of  igni- 
tion, and  in  a  minor  way  on  several  other 
conditions  which  are  not  of  sufficient  im- 
portance to  consider  at  present.  If  the 
mixture  contains  the  most  effective  pro- 
portion of  gas  and  air,  and  the  ignition  is 
properly  timed,  as  it  should  be,  it  leaves 
the  matter  of  compression  and  quality  of 
fuel  as  the  two  important  points  to  be  con- 
sidered, with  reference  to  the  M.  E.  P.  The 
highest  mean  effective  pressures  are  those 
obtained  with  natural  gas  and  gasoline, 
then  come  the  illuminating  gases  in  the 
order  of  their  light-giving  values— water- 


gas  and  semi-water-gas  —  the  latter  being 
usually  known  as  producer-gas.  For  the 
compression  pressure  usually  employed,  the 
M.  E.  P.s  range  between  45  Ib.  per  sq.  in. 
and  80  Ib.  per  sq.  in.,  with  the  average  not 
far  from  65  Ib.  per  sq.  in.  for  an  average 
quality  of  natural  gas.  For  gasoline  the 
M.  H.  P.  may  safely  be  taken  at  70  Ib.  per  sq. 
in.  The  author  has  found  the  following 
formulas  are  very  well  borne  out  in  practice 
for  the  best  performance  of  the  average 
gas  engine  : 

Let  D  =  the  diameter  of  the  cylinder  in 
inches  ; 

L  =  the  length  of  the  stroke  in  inches  ; 

R  =  the  number  of  revolutions  per  min- 
ute ; 

Then  for  a  four-cycle  engine 


19,000 

For  a  two-cycle  engine 
' 


IO,OOO 

For  engines  using  gasoline  these  denom- 
inators should  be  reduced  to  18,000  and 
9,500  respectively.  These  formulas  may  be 
used  for  determining  the  dimensions  of 
any  engine  that  is  being  designed,  if  the 
performance  of  any  engine  of  the  same 
kind  and  on  the  same  quality  of  fuel  is 
already  known.  The  denominator  of  the 


fraction   then  becomes  an  unknown  quan- 
tity and  it  may  be  found  as  follows : 

Calling  the  unknown  denominator  A' 

X  =         X  -^  X  ^  /  \ 

(D.  H.  P.) 

Suppose  an  engine  which  is  a  good  ex- 
ample of  a  series  already  being  built  has  a 
cylinder  2O//  diameter  and  a  stroke  of  3O/X, 
i.  e.,  a  20XXX  30XX  engine,  and  that  it  runs  at 
120  r.  p.  m.  giving  70  D.  H.  P.,  the  value  of 
Xis 

v=  (20)2  X    30    XI20         _ 

— ^-  20,577  -1 

call  X  20,600. 

The  formula  fer  these  engines  is  then 

nz  v   7    v    I? 
D.  H.   P.  =          A  ^  A   ^ 

20,600 

To  find  the  diameter  of  the  cylinder  for 
any  engine  to  give  a  required  horsepower 
at  a  given  speed,  the  ratio  of  the  stroke  to 
the  diameter  should  first  be  determined. 
For  a  four-cycle  engine,  prominent  author- 
ities agree  that  the  best  proportion  is  to 
make  the  stroke  ij^  times  the  cylinder 
diameter.  For  a  two-cycle  engine,  practice 
varies  between  making  the  diameter  of  the 
cylinder  and  the  stroke  the  same,  to  a  stroke 
equal  to  i^  times  the  diameter.  It  is  also 
necessary  to  decide  upon  the  speed  at 
which  the  engine  shall  run.  Gas  engines 
built  in  the  United  States,  are  seldom  run 


at  a  higher  piston  speed  for  horizontal  en- 
gines than  600  feet  per  minute  and  for 
vertical  engines  700  feet  per  minute.  The 
following  formulas  representing  average 
practice  among  manufacturers  will  be  found 
valuable  in  making  the  first  approximate 
calculation  : 

Let  H  =  the  D.  H.  P.  of  the  engine  ; 

Let  R  =  the  rev.  per  min.  ; 

Then  for  a  four-cycle  engine  A*  =-^  —     ' 

"    "  two-cycle        "       R  =  -44°.     W 

« 


In  order  to  solve  the  above  two  equations 
it  is  necessary  to  use  logarithms.  Suppose 
it  is  'desired  to  find  the  speed  of  a  fifteen- 
horsepower  four-cycle  engine.  Take  a  table 
of  logarithms  and  find  first  the  logarithm 
of  15,  which  is  1.176091  ;  multiplying  by  .21 
the  result  is  .24697911,  which  is  the  log  of 
15  to  the  .21  power.  The  log  of  380  is 
2.579784;  subtracting  the  log  of  (i5)-21  from 
this—  2.579784 
.246979 
2.332705  =  log  215-1  + 

And  the  proper  speed  for  this  engine 
would  be  215  r.  p.  m.  or  thereabout.  For  a 
four-cycle  engine,  formula  (6)  gives  a  piston 
speed  of  600  feet  per  minute  at  32.5  horse- 

125 


power,  and  for  a  two-cycle  engine,  formula 
(7)  gives  a  piston  speed  of  600  feet  per  min- 
ute at  71  horsepower.  Beyond  these  powers, 
the  formulas  (6)  and  (7)  should  not  be  used 
but  the  computations  made  from  the  piston 
speed.  At  600  feet  piston  speed  the  r.  p.  m. 
is  found  as  follows  : 

(8) 


JL, 

When  the  piston  speed  of  the  engine  is 
600  feet  per  minute,  much  simpler  formu- 
las than  (3)  and  (4)  may  be  used  to  find  the 
diameter  of  the  cylinder.  Using  the  same 
value  of  X  as  before, 

D  =  2.3  ^/  H  for  a  4-cycle  engine  ;  A'  = 
19,000.  (9) 

D  =  i.67/y/  H  for  a  2-cycle  engine  ;  X  = 
10,000.  (  10) 

These  formulas  should  not  be  used  ex- 
cept for  a  piston  of  speed  of  600  feet  per 
minute.  The  stroke  of  the  engine  can 
afterwards  be  determined  by  its  ratio  to 
the  diameter,  and  from  that  the  r.  p.m.  may 
be  found  by  means  of  formula  (8).  It  should 
be  remembered  that  these  equations  are 
applicable  as  they  stand,  only  for  engines 
with  one  cylinder.  When  the  engine  is  to 
be  built  with  two  or  more  cylinders,  the 
horsepower  must  be  divided  by  the  number 
of  cylinders.  Thus,  if  a  three-cylinder  en- 

126 


glne  of  45  horsepower  is  to  be  designed,  the 
calculations  for  cylinder  diameter,  r.  p.  m., 
etc.,  should  be  made  for  a  i5-horsepower 
engine. 

Should  the  reader  desire  to  calculate  the 
power  of  a  gas  engine  from  a  known  M.  B. 
P.,  the  following  formulas  will  assist  him. 
When  the  piston  speed  is  600  feet  per  min- 
ute and  the  stroke  of  the  piston  is  i^  times 
its  diameter 


p 

Wherein  P  =  the  M.  B.  P. 
When   the   piston    speed  is  700  feet  per 
minute 

D=  1.55  V1-  H-p-  (I2) 

~P 

Both  of  these  formulas  are  for  the  4-cycle 
engine.  If  it  is  desired  to  find  the  D.  H.  P., 
an  M.  B.  of  80%  may  be  safely  employed 
for  engines  under  25  horsepower.  For 
larger  engines  having  two  or  more  cylin- 
ders 85%  may  be  used.  The  reason  that  a 
higher  efficiency  may  be  obtained  from 
multiple  cylinder  engines,  is  that  the  fly- 
wheels are  much  lighter,  and  the  load  is 
better  distributed  throughout  a  revolution, 
reducing  the  friction  of  the  engine.  It  is 
fast  becoming  the  custom  to  build  engines 
larger  than  50  D.  H.  P.  with  two  or  more 

127 


cylinders.  Although  four-cylinder  engines 
have  been  built  and  are  in  use,  it  is  the 
opinion  of  many  gas-engine  experts  that 
no  material  advantage  is  gained  by  increas- 
ing the  number  of  cylinders  beyond  three. 
The  cylinder  diameter  of  a  gas  engine 
may  be  made  the  basis  of  nearly  all  other 
dimensions  of  the  engine  and  not  make 
them  vary  but  a  few  percent  from  what 
would  be  given  by  the  best  of  formulas. 
Although  every  dimension  of  the  engine 
should  rightly  be  discussed  in  the  present 
chapter,  the  author  will  give  each  part  a 
chapter  by  itself  in  order  to  make  them 
easier  of  reference. 


128 


CHAPTER  XVI. 

THE    CYLINDER. 

A  good  example  of  a  gas-engine  cylinder 
is  shown  in  Fig.  27.  The  dimensions  of 
the  various  parts  have  been  based  upon 
average  practice  of  gas-engine  designers  in 
this  country,  and,  although  he  will  not  be 
able  to  take  up  any  gas-engine  design  he 
chances  to  come  across  and  find  the  di- 
mensions exactly  fitting  these  formulas,  he 
will,  by  the  use  of  the  following  equations, 
be  able  to  produce  a  design  which  will  be 
in  good  proportion. 

For  the  thickness  of  the  cylinder  wall  it 
is  necessary  to  allow  for  reboring  to  a  cer- 
tain extent,  and  also  to  have  sufficient  metal 
for  stiffness,  and  to  make  a  good  casting 
when  the  cylinder  is  a  small  one.  The 
thickness  of  the  wall  is  therefore  made 
quite  a  little  heavier  than  is  necessary  for 
mere  resistance  to  pressure.  The  following 
formula  is  that  which  represents  average 
practice. 

I2Q 


/=.o9/>;       (13) 

Wherein  t  =  the  thickness  of  the  cylinder 

wall ; 

D  —  the  diameter  of  the  cylinder. 
The  depth  of  the  water-jacket  is  usually 
as  given  by  the  following  formula : 

y=..i/V     (M) 

Wherein/  =  the  depth  of  the  water-jacket. 
This  depth  is  measured  on 
a   radius    of    the    cylinder 
across  the  water-jacket. 
No  regular  proportion  appears  to  be  fol- 
lowed at  all  closely  for  the  thickness  of  the 
outer  wall  of  the  water-jacket.     The  author 
has  used  for  engines  of  his  own  design  a 
thickness  which  is  half  that  of  the  cylinder 
wall,  or  .045  D. 

For  very  small  engines  these  formulas 
give  dimensions  which  produce  walls  too 
thin  for  the  foundryman.  In  order  to  get 
good  castings  it  is  well  to  limit  the  thick- 
ness of  the  cylinder  wall  to  T5g-  inch,  the 
depth  of  the  water-jacket  to  y%  inch,  and  the 
thickness  of  the  jacket  wall  to  %  inch. 

In  order  to  find  the  diameter  of  the  cyl- 
inder head  studs  the  maximum  pressure 
within  the  cylinder  must  be  known  as  well 
as  the  number  of  studs.  It  is  a  good  plan 
to  limit  the  distance  between  the  studs  to 
six  inches,  unless  there  is  a  feature  in  the 
design  of  the  cylinder  or  the  head  that  will 


prevent  such  a  space  being  used.     An  even 
number  of  studs  is  almost  invariably  em- 
ployed.    The  following  formula  should  be 
used  for  finding  the  diameter  of  the  stud  : 
L,et  A  =  the  diameter  of  the  cylinder  ; 
z  =  the  diameter  of  the  stud  at  the 

root  of  the  thread  ; 
S1  —  the  safe  stress  in  Ib.  per  sq.  in.; 
p  =  the   maximum  pressure   in   the 

cylinder  ; 
n  =  the  number  of  studs  ; 


Then  </«=          or  d  =  D\JL_.        (15) 


sn 


sn 


The  flange  by  which  the  cylinder  is  at- 
tached to  the  frame,  may  be  either  square 
or  circular.  It  is  usually  square  on  vertical 
engines  and  circular  when  the  cylinder  is 
horizontal.  The  sizes  of  the  bolts  which 
are  used  to  fasten  the  cylinder  to  the  frame 
may  be  found  by  formula  (15)  making  z  the 
diameter  of  the  bolt  at  the  root  of  the 
thread  and  n  the  number  of  bolts.  The 
thickness  of  the  cylinder  wall  between  the 
end  of  the  water-jacket  and  the  flange 
should  be  .125  D.  The  thickness  of  the 
flange  should  be  equal  to  the  diameter  of 
the  bolt  -f-  %".  On  engines  smaller  than 
six  horsepower,  it  is  customary  to  make  the 
cylinder  and  the  frame  in  one  casting.  The 
water-jacket  should  extend,  beyond  the  end 
of  the  piston  nearest  the  cylinder  head,  tc 

132 


H  :^^^^^^N^\\^^^^\v^ 

^\^\\\xs\\x\i  i? 

i  i        a 

JSJSSSE^SXSSSS^B 

g  gy 

^^^ix^^vj 

00 
c* 


133 


a  distance  equal  to  about  10%  of  the  stroke. 
The  size  of  the  water  inlet  and  outlet  pipes 
should  be  .15  times  the  diameter  of  the  cyl- 
inder. 

Two  methods  are  in  use  for  making  the 
core  for  the  water-jacket  space.  In  one  the 
core-box  consists  of  two  cylinders  of 
wrought  iron,  placed  one  within  the  other 
and  of  the  proper  dimensions  to  make  the 
space  between  them  equal  to  the  size  of  the 
core.  The  core  is  then  rammed  up  between 
the  two  cylinders  and  put  into  the  core- 
oven  in  the  core-box.  With  this  method  of 
making  the  cores  there  is  no  necessity  of 
making  draft  in  the  core-box  for  the  metal 
about  the  studs.  Another  method  of  mak- 
ing the  core  is  to  make  one  half  of  the  core 
at  a  time,  using  the  same  core-box  for  each 
half,  the  core  being  lifted  out  sideways. 
With  this  form  of  core-box  it  is  necessary 
to  arrange  the  metal  as  shown  by  the  dot- 
ted lines  in  the  figure  in  order  to  make  a 
draft  on  the  parts  y  y. 

The  cylinder  head,  when  it  contains  no 
valves  or  other  mechanism,  is  made  as 
shown  in  Fig.  28.  The  formulas  for  the 
thicknesses  of  the  walls  and  the  depth  of 
the  water-jacket  are  the  same  as  for  the 
cylinder.  In  fact,  it  may  be  said  to  be  an 
extension  of  the  cylinder.  In  some  engines 
the  end  of  the  cylinder  is  closed  and  is 


made  in  the  form  of  a  sphere.  In  others 
the  cylinder  is  closed  but  a  head  is  used  to 
cover  the  end  of  the  cylinder  in  such  a 
manner  that  it  forms  the  outer  wall  of  the 
water-jacket  at  that  point.  In  many  en- 
gines, the  valves  are  placed  in  the  head 
while  in  others,  the  head  contains  but  one 
valve  or  the  igniter. 


135 


CHAPTER  XVII. 

VALVES  AND  VALVE-BOXES. 

The  methods  employed  for  handling  the 
charge  and  the  exhaust  was  discussed  in 
Chapter  X.  The  proportions  of  the  valve 
passages,  the  valves  and  the  valve-boxes 
will  be  discussed  in  the  present  chapter. 
The  proportions  of  the  passages  for  both 
the  entering  charge  and  the  exhaust  should 
be  founded  upon  the  speed  at  which  the 
gases  will  be  compelled  to  pass  through 
them.  Hence  the  areas  of  these  passages 
depend  upon  both  the  area  of  the  cylinder 
and  the  speed  of  the  piston.  Too  frequently 
these  areas  are  made  smaller  than  they 
should  be,  with  a  consequent  wire-drawing 
and  loss  of  power.  A  careful  discussion  oi 
this  matter  with  prominent  designers,  both 
in  this  country  and  in  Europe,  shows  the 
concensus  of  expert  opinion  to  be,  that  the 
speed  of  the  gases  should  be  limited  to  loc 
feet  per  second  in  the  inlet,  and  to  85  fee' 

136 


per  second  in  the  exhaust  passages.  The 
85  feet  per  second  allowance  for  the  exhaust, 
is  made  on  the  assumption  that  the  prod- 
ucts of  combustion  are  driven  from  the  cyl- 
inder when  at  atmospheric  pressure,  this 
assumption  being  made  for  convenience 
only.  As  a  matter  of  fact  the  pressure  of 
the  gases  at  the  moment  of  release  range 
between  30  and  40  lb.,  and  the  lower  limit 
of  speed  for  the  gases  in  the  exhaust  pas- 
sages is  adopted  for  this  very  reason.  As 
the  piston  speed  of  gas  engines  varies  con- 
siderably, even  for  engines  of  the  same 
power  when  built  by  different  manufactur- 
ers, it  should  always  be  taken  into  consid- 
eration when  proportioning  the  passages. 
It  should  also  be  remembered  that  to  make 
the  areas  of  the  inlet  and  the  exhaust  pipes 
according  to  the  above,  and  to  then  choke 
the  column  of  gas  by  a  small  valve  opening 
or  cylinder  port,  is  not  very  good  practice. 
The  formulas  given  below  will  give  the  de- 
signer a  short  method  of  determining  the 
sizes  of  the  passages  : 

Let  .9  =  the  speed  of  the  piston  in  feet  per 
minute ; 

A.  =  the  area  of  the  cylinder ; 

a  =  the  area  of  the  inlet  passages  ; 

a1  =  the  area  of  the  exhaust  passages; 

D  =  the  diameter  of  the  cylinder; 

d  =  the  diameter  of  the  inlet  passage  ; 

137 


-p- 


-  — /i— 


dl  =  the  diameter  of  the  exhaust  pas- 

sage ; 

L       the  length  of  the  stroke  in  inches  ; 
R  =  the  r.  p.  m.  of  the  crankshaft; 
then 

(16)   ora  =  ARL    (i6a)    for 


- 
6,000  36,000 

the  inlet. 

l=  -—(17)  or  a1  =    ARL    (lya)    for/ 
5,100  30,600 

the  exhaust. 


for  the  inlet  (i6b). 

d  l  =  .  00572/2  ^  /?/,  for  the  exhaust  (lyb) 
When  the  piston  speed  of  the  engine  is  at 
the  usual  limit  for  horizontal  engines  these 
formulas  may  be  still  further  simplified  to  : 

a       .1  A  (i6c); 

a1  =  .12  A  (iyc)  ; 
and  for  passages  of  circular  cross-section  to 


dl  =  .35  D  (i7d). 

The  designer  should  use  the  formula  best 
suited  to  his  work  and  he  will  find  that,  in 
many  cases,  he  may  calculate  the  dimen- 
sions by  one  formula  and  use  another  as  a 
check. 

The  proportions  of  the  valve  are  shown 
in  Fig.  29.  The  author  does  not  insist  that 
these  proportions  should  be  followed  in 
every  case  but  they  form  a  very  convenient 

139 


140 


basis  for  the  design  of  a  valve,  especially  in 
those  cases  where  it  is  hard  for  the  designer 
to  decide  what  to  do,  as  the  ratios  suggested 
below  will  give  a  valve  of  good  proportion. 
The  dimensions  are  based  upon  the  diam- 
eter of  the  opening  as  a  unit.  They  are  : 

V=  1.14  d; 

b  =  .14  d\ 

c--=  .07  tf; 

s  -=  .2  d,  for  short  stems ; 

s  -=  .23  d,  for  long  stems ; 

r  =  .25  d,  the  minimum  lift  of  the  valve, 
to  which  should  be  added  J^  inch  to  allow 
for  wear. 

At  B  is  shown  the  usual  method  of  mak- 
ing an  exhaust  valve,  the  head  of  the  valve 
being  riveted  to  the  stem.  This  is  neces- 
sary because  the  head  of  the  exhaust-valve 
should  be  made  of  cast  iron,  as  wrought 
iron  or  steel  will  not  stand  the  abrasive 
action  of  the  hot  gases. 

Three  methods  of  arranging  the  valves  011 
the  engine  are  shown  in  Figs.  30,  31  and  32. 
Fig.  30  is  a  cylinder  head  arranged  for  both 
the  inlet  and  the  exhaust-valve,  and  the 
proportions  of  the  various  dimensions  to 
the  cylinder  diameter  are  marked  upon  the 
different  parts.  It  is  always  a  good  practice 
to  water-jacket  the  exhaust-valve,  so  that 
the  heat  may  be  carried  away  from  both 
the  bearing  for  the  stem  and  the  valve-seat. 

141 


142 


In  the 


11  the  figure,  the  inlet-valve  is  also  shown 
water-jacketed.  It  is  not  necessary  to  jacket 
the  inlet-valve,  as  the  incoming  air  suffices 
to  keep  it  cool.  The  jacket  is  continued 
about  the  valve  in  this  case,  in  order  to  save 
iron  and  to  retain  a  uniformity  of  construc- 
tion. 

In  Fig.  31  is  shown  a  valve-box  designed 
to  be  attached  to  the  side  of  the  cylinder 
and  to  so  place  both  valves  that  their  stems 
are  parallel  and  point  in  the  same  direction. 
This  box  is  a  style  used  on  both  horizontal 
and  vertical  engines  and  is  employed  where 
the  camshaft  is  at  a  right  angle  to  the  axis 
of  the  cylinder  and  between  the  valve-box 
and  the  crankshaft.  In  order  that  the 
valves  may  be  removed  from  the  box  with- 
out taking  them  apart,  openings  are  made 
in  the  box  at  Jt  and  S  and  the  holes  are 
closed  with  a  cap  A.  The  cap  is  fitted  to 
the  box  with  a  ground  joint  and  is  held  in 
place  by  the  clamp  B.  The  proportions  of 
the  various  parts  of  the  box  are  shown  by 
formulas  on  the  figure.  But  one  view  of 
the  box  is  shown,  a  cross-section  through 
the  axes  of  the  valves.  It  is  bolted  to  the 
cylinder  by  means  of  studs  passing  through 
the  holes  j,  the  studs  serving  also  to  hold 
the  cover  of  the  box.  The  inlet  gases  enter 
through  a  cored  passage  in  the  cylinder  and 
the  opening  /,  from  whence  they  pass 

143 


144 


through  the  inlet-valve  to  the  cylinder-port 
P.  From  the  port  P  the  products  of  com- 
bustion pass  through  the  exhaust-valve 
opening  to  E  and  through  to  a  cored  ex- 
haust passage  in  the  cylinder. 

Fig.  32  is  an  illustration  of  a  valve-box  so 
arranged  us  to  place  both  valves  in  a  box  of 
the  smallest  possible  compass.  .The  ex- 
'haust-valve  is  operated  by  means  of  a  cam, 
but  the  inlet-valve  is  intended  to  be  ope- 
rated by  the  suction  of  the  engine  piston. 
The  box  is  shown  in  section  through  the 
plan.  In  order  to  permit  of  removal  of 
the  valves,  the  seat  for  the  inlet-valve  and 
the  bearing  for  its  stem  are  placed  in  a 
separate  casting,  which  is  bolted  to  the  box 
as  shown.  The  opening  from  the  valve- 
box  into  the  cylinder  is  shown  at  B  and 
from  the  jacket  surrounding  the  exhaust- 
valve  to  the  jacket  of  the  cylinder  at  A. 
The  exhaust-valve  opening  is  shown  at  E 
and  the  inlet-valve  opening  at  /.  The  ex- 
haust-valve is  bolted  to  the  box  by  means  of 
a  flange,  while  the  inlet  is  screwed  into  the 
side  of  the  cover  at  C.  It  would  be  well  to 
put  a  union  into  the  inlet  pipe  near  the  box, 
in  order  that  the  cover  may  be  taken  off 
without  difficulty.  The  dimensions  of  the 
the  various  parts  of  the  box  are  shown  b} 
equations  on  the  figure,  as  in  Figs.  30  and  31, 

u.s 


CHAPTER  XVIII. 

THE    PISTON,  THE    COXXECTING-ROD 
AND    THE    CRANKSHAFT. 

With  few  exceptions,  all  gas  engines  are 
fitted  with  trunk-pistons.  The  principal 
reason  for  the  adoption  of  the  trunk-piston 
is,  that  if  the  engine  were  made  double-act- 
ing, as  are  most  of  the  steam  engines,  the 
hot  gases  would  surround  the  piston-rod 
heating  it  to  a  temperature  that  would  cause 
it  to  cut  in  the  stuffing-box.  The  trunk 
piston  taking  an  impulse  on  the  end  where 
there  would  be  no  rod  were  the  engine 
double-acting,  gives  no  trouble  from  this 
source.  As  the  other  end  of  the  cylinder  is 
not  used,  there  is  no  necessity  for  closing  it, 
and  by  making  the  piston  long  enough  to 
act  as  a  guide,  there  is  no  need  for  either  a 
piston-rod  or  a  cross-head.  A  few  engines 
are  manufactured  which  are  double-acting, 
the  trouble  from  an  overheated  piston-rod 
being  avoided  by  providing  means  for  cool- 
ing the  rod.  In  one  of  these  engines  the 
water-jacket  is  extended  so  that  it  surrounds 

146 


ie  stuffing-box,  while  in  another,  the  rod 
is  made  hollow  and  water  is  circulated 
through  it. 

The  present  discussion  will  be  confined 
entireh-  to  the  trunk-piston.  For  a  treat- 
ment of  the  piston  for  the  double-acting 
engine,  the  reader  is  referred  to  works  on 
steam-engine  design.  An  example  of  the 
trunk-piston,  as  usually  employed  with  the 
gas  engine,  is  shown  in  Fig.  33.  The  pro- 
portions are,  with  the  exception  of  the 
pin,  based  upon  the  cylinder  diameter  as  a 
unit.  All  the  necessary  equations  are  placed 
upon  the  drawing.  For  small  pistons  of  S" 
diameter  and  under,  the  ribs  R  may  be 
omitted,  and  the  piston  designed  as  shown 
by  the  dotted  line.  In  some  engines  there 
is  a  supplementary  piston-ring  added,  as 
shown  by  the  dotted  lines  at  Z.  Up  to  and 
including  pistons  \Q"  diameter  three  rings 
will  be  found  sufficient.  For  sizes  above  S", 
four  rings  should  be  used,  one  of  which 
may  be  placed  as  shown  at  Z.  In  pistons 
above  \2"  diameter  four  rings  should  be 
placed  between  the  pin  and  the  inner  end. 
and  a  fifth  ring  added  at  Z  if  it  is  desired  to 
place  a  ring  at  this  point.  The  extra  ring 
is  of  somewhat  doubtful  utility,  so  far  as 
the  packing  ring  Z  is  concerned.  It  is  con- 
tended by  some  that  it  relieves  the  piston  of 
pressure  on  the  cylinder,  but  as  the  piston 

U7 


N 

—  i  —                 — 
N 

a 


148 


is  not  in  any  way  supported  by  the  rings,  it 
is  difficult  to  see  what  foundation  there  is 
for  such  an  argument.  In  using  the  equa- 
tions given  in  Fig.  33,  the  designer  should 
be  careful  to  observe  the  limits,  on  the 
smaller  sizes,  that  it  is  necessary  to  consider 
for  securing  good  castings.  The  piston 
wall  should  not  be  less  than  T\x/,  and  even 
then  the  pattern  should  allow  considerable 
stock  to  be  turned  out  in  the  lathe.  The 
difference  in  the  thickness  of  the  rings  at 
the  smaller  and  the  larger  ends  may  be  less 
or  more  than  T^x/  according  to  the  method 
of  turning  them  up.  A  ring  which  would 
be  of  equal  strength  throughout  would 
taper  off  to  nothing  at  the  smaller  end.  In 
the  shop  when  turning  piston-rings  for  a 
gas  engine,  some  method  should  be  followed 
whereby  the  outside  of  the  ring  is  turned  to 
a  perfect  circle,  the  diameter  of  which  shall 
be  exactly  the  same  as  the  bore  of  the  cylin- 
der. In  order  to  do  this  it  is  necessary  to 
first  cut  the  rings  a"nd  then  to  clamp  them 
in  a  jig  which  will  hold  them  sprung  very 
nearly  together.  The  ring  is  then  turned 
to  the  diameter  of  the  cylinder  while  held 
in  the  jig.  This  is  the  secret  of  securing  a 
tight  piston,  and  one  that  will  successfully 
withstand  the  high  pressures  due  to  the 
increase  in  compression,  which  is  now  so 
extensively  coming  into  use. 

149 


"^iiftiz 


The  diameter  p  of  the  piston-pin  should 
be  determined  by  the  bearing  surface  re- 
quired ;  the  length  of  the  pin  should  ber 
wherever  possible,  the  same  as  that  of  the 
crank-pin.  The  average  pressure  which  is 
allowable  upon  the  piston-pin  per  sq.  in.  of 
projected  area  is  7.50  Ibs.  In  order  to  find 
the  diameter  of  the  pin,  when  the  length  is 
known,  the  designer  may  make  use  of  the 
following  equation. 

f=  — —         (l8) 
750  Xe 

Wherein  p  =  the  diameter  of  the  piston 
pin ; 

A  =  the  area  of  the  cylinder : 

P  =  the  M.  B.  P. ; 

e  =  the  length  of  the  piston  pin. 
The  connecting-rod  of  a  gas  engine  is 
made  in  various  styles,  but  what  is  known 
as  the  marine  type,  and  illustrated  in  Fig. 
34,  is  that  in  most  general  use.  This  rod  is 
of  circular  cross-section  and  is  easily  ma- 
chined, as  it  is  nearly  all  of  it  turned  in  the 
lathe.  It  is  made  slightly  tapering,  the 
larger  end  being  that  nearest  the  crank-pin. 
The  taper  given  is  dependent  to  some  ex- 
tent upon  the  length  of  the  rod,  the  crank 
end  being  from  ^^  to  ^"  larger  than  the 
piston  end.  Thus,  for  a  24"  rod  the  differ- 
ence would  be  ^''^  and  on  a  60"  rod  a  dif- 
ference of  Y%" ,  or  a  difference  of  }/%"  for 


?ach  foot  between  centers.  The  mean  di- 
ameter of  the  rod,  /.  ^.,  the  half  sum  of  the 
diameters  of  the  two  ends  may  be  found  by 
means  of  the  formula  given  below. 


r  =  .035  \/w;        (19) 

Wherein  r  =  the  mean    diameter  of  the 
rod  ; 

D  =  the  diameter  of  the  cylinder  ; 
/  =  the   length   of   the   rod   be- 
tween centers  in  inches  ; 

m  =  the  maximum    pressure 

within  the  cylinder  in  Ib.  per  sq.  in. 

For  the  convenience  of  the  designer  the 

author  has  deduced  the  following  formulas 

for  the  mean  diameter  for  engines  in  which 

the  stroke  is  i%  times  the  diameter  of  the 

cylinder.    When  /  =  2£,  L  being  the  length 

of  the  stroke, 

r==   .06  D  i/  m     (19  a) 

When  /  2.5  L,  r  =  .068  1)  \/-^  (19  b) 
l=$L,  r  ===  .074  D  j1/"^"  (19  c) 

These  formulas  may  be  still  further  sim- 
plified by  extracting  the  fourth  root  of  m 
for  a  range  of  pressures  within  ordinary 
use.  Thus,  when  /  =  2/,  and  m  is  240  Ib. 
per  sq.  in.  r  »  .236  D. 

Call  the  coefficient  of  D  in  this  equatioi: 
/'"and  the  formula  becomes  r  =*  FD.  (19  d] 

The  values  of  F  for  various  proportions 
of  /  and  L  and  for  different  values  of  m  an 

152 


given  in  the  following  table.  The  designer 
may  take  the  values  nearest  to  those  he 
expects  to  use,  and  from  these  find  the  di-. 
mension  of  r. 

When  7=2/.     When  7=2.5^    When  7=3/, 

;;/  /v   .  F=^  F  = 

240  .236  .268  .291 

280  .245  .277  .303 

320  .253  .288  .313 

360  .261  .296  .322 

400  .268  .304  .331 

The  proportions  of  the  various  dimen- 
sions of  the  brasses,  etc.,  to  sizes  of  the 
pins  are  shown  on  the  figure. 

The  crankshaft  of  a  gas  engine  has  to 
withstand  not  only  the  strain  due  to  the 
transmission  of  the  entire  power  of  the 
engine,  but  this  strain,  at  the  time  it  conies 
upon  the  shaft,  is  equal  to  four  times  the 
average  power  transmitted.  This  is  one 
reason  why  the  crankshaft  of  a  gas  engine 
must  be  so  much  larger  than  that  of  a  steam 
engine  of  the  same  power.  To  find  the  di- 
ameter of  the  crankshaft,  the  diameter  of 
the  cylinder  and  the  maximum  pressure 
within  the  cylinder,  is  taken  as  the  basis  of 
computation. 

Let  6"= the  diameter  of  the  crankshaft ; 

D  and  m  as  above  ; 

Then  for  steel  ,£-—.059  D  f/~f^         (20) 
For  wrought  iron  ,V  —.064  D  i^"^T      (20  a) 


153 


These  formulas  are  lor  the  average  case 
of  L  =  i%  D.  When  there  is  much  of  a 
departure  from  this  ratio  the  following  for- 
mula should  be  used : 

For  wrought  iron, 

5=  .056  ^~^ZJ9a~  (20  *) 
For  steel,  S=  .052  f  m  L  D*  (20  c) 
These  formulas  will  give  somewhat  larger 
crankshafts  than  are  in  use  on  many  gas 
engines,  but  it  is  a  matter  worthy  of  note 
that  too  many  crankshafts  are  made  too 
small.  The  diameter  of  the  crankpin  is  usu- 
ally made  i^  times  that  of  the  crankshaft. 
Practice  varies  in  this  respect  from  making 
the  pin  the  same  diameter  as  the  shaft  to 
1.25  times  the  shaft.  It  is  a  good  plan  to 
select  the  larger  rather  than  the  smaller 
ratio.  Mr.  Frederick  Grover,  an  English 
writer,  recommends  the  ratio  1.2  as  the 
lowest  limit.  It  should  be  remembered  that 
the  larger  the  diameter  the  shorter  the  pin. 
The  projected  area  of  the  crankpin  should 
be  such  that  the  average  pressure  does  not 
exceed  400  Ib.  to  the  sq.  in.  From  this  the 
following  formula  is  derived  : 

/=  dJ?     («j 

400^7 

Wherein  q  =  the  diameter  of  the  pin  ; 
fr=  the  length  of  the  pin  ; 
A  and  P  as  in  formula  (18). 


I 
o- 


-b— + 


155 


The  length  of  the  crankshaft  bearing  is 
usually  from  2S  to  2.5,5",  the  smaller  ratio 
2S  being  that  in  most  general  use.  Fig.  35 
shows  a  good  example  of  a  crankshaft  with 
those  proportions  not  already  given,  marked 
upon  the  figure. 


156 


CHAPTER  XIX. 

THE     ENGINE     FRAME. 

As  with  many  other  parts  of  the  gas  en- 
gine, the  frame  is  built  in  so  many  different 
styles  that  to  give  an  example  of  every  one 
would  take  up  more  room  than  is  at  the 
disposal  of  the  author  in  this  work. 

A  good  example  of  the  style  of  frame  in 
use  on  a  great  many  horizontal  gas  engines 
is  shown  in  Fig.  36,  writh  the  proportions  of 
the  various  parts  shown  by  their  relation  to 
the  cylinder  diameter  of  the  engine.  The 
angle  of  the  parting  line  of  the  bearing 
brasses  is  taken  at  45°,  in  order  that  the 
thrust  of  the  piston  may  not  come  directly 
against  the  stud,  but  against  the  frame. 
The  most  rational  angle  for  the  parting 
line  would  be  at  90°  to  the  resultant  of  the 
average  total  pressure  of  the  piston  and 
that  of  the  flywheels.  This  would,  however, 
make  the  angle  a  very  steep  one,  and  it 
makes  a  much  neater-looking  design  to 
make  the  angle  as  shown,  while  keeping 

157 


If 


158 


the  pressure  of  the  thrust  from  the  piston, 
on  the  frame.  The  cylinders  of  gas  engines 
are  quite  frequently  cast  with  projections 
on  the  side,  by  which  they  are  bolted  to 
the  frame,  as  shown  in  cross-section  at  Z. 
It  is  claimed  that  the  overhanging  piston 
will  not  get  out  of  shape  when  the  tem- 
perature rises  while  the  engine  is  at  work. 
The  author  must  confess  that  he  has  been 
unable  to  detect  any  difference  in  the  effect 
upon  the  cylinders  with  an  engine  built  by 
either  method.  In  some  engines  the  frame 
is  set  directly  on  the  foundation,  while  with 
others  a  sub-base  is  furnished,  which  is 
practically  a  continuation  of  the  frame.  It 
is  usual  to  make  the  lower  part  of  the  frame 
hollow  when  there  is  no  base,  and  to  draw 
the  air  supply  from  this  space  in  order  to 
vmake  the  suction  a  quiet  one.  When  there 
is  a  base,  the  air  is  drawn  from  the  hollow 
portion  of  the  base. 


159 


CHAPTER  XX. 

FLYWHEELS. 

The  great  proportion  of  idle  strokes  to 
those  in  which  work  is  actually  being  done 
upon  the  piston  makes  it  imperative  that 
the  gas  engine  be  supplied  with  a  very 
heavy  flywheel  in  order  to  regulate  the 
speed  within  reasonable  limits.  For  dif- 
ferent requirements  in  speed  regulation 
there  will  be  a  difference  in  the  weight  of 
the  flywheel.  Steadiness  of  speed  is  usually 
spoken  of  as  percent  variation,  for  the  rea- 
son that  there  is  no  such  thing  as  absolute 
uniformity  of  speed,  but  a  variation  between 
limits  that  is  determined  by  the  efficiency 
of  the  governor  mechanism  and  the  regu- 
lating power  of  the  flywheel.  Thus,  a  gas 
engine  that  is  operating  with  a  speed  vari- 
ation of  2%  and  at  an  average  speed  of  200 
r.  p.  m.,  has  a  difference  between  the  high- 
est and  the  lowest  speed  of  the  engine 
occurring  between  one  impulse  stroke  and 

1 60 


;he  next,  of  200  X-°2— 4  revolutions;  and 
since  the  average  speed  of  the  engine  should 
be  200  r.  p.  m.,  the  speed  should  vary  be- 
tween 202  r.  p.  m.  and  198  r.  p.  m.  It  is  as 
well  to  note,  at  this  point  in  the  discussion, 
a  mistake  that  is  occasionally  made.  This 
is,  to  consider  the  steadiness  of  speed  as 
the  percent  of  difference  of  speed  between 
no  load  and  full  load.  To  illustrate  :  If  the 
engine  ran  at  220  r.  p.  m.  at  no  load,  and  at 
212  r.  p.  m.  at  full  load,  then  the  speed  va- 
riation would  be  considered  as  220 — 212=8 
r.  p.  m.,  and  the  engine  said  to  regulate 
within  8-^-216=3.7%"  nearly.  A  little  reflec- 
tion will  show  that  the  steadiness  of  motion 
is  not  to  be  determined  by  the  difference 
between  the  speeds  at  no  load  and  at  full 
load,  this  matter  being  one  that  is  depend- 
ent in  a  great  measure  upon  the  regulating 
power  of  the  governing  mechanism ;  or,  in 
other  words,  upon  the  efficiency  of  the  gov- 
ernor. The  steadiness  of  speed  between 
one  impulse  and  the  next  is  dependent 
entirely  upon  the  power  for  storing  energy 
that  is  contained  not  only  in  the  flywheel 
of  the  engine  but  in  the  moving  parts  of 
the  machinery  it  is  driving.  Thus,  the  ar- 
mature of  a  dynamo  adds  somewhat  to  the 
power  of  storing  energy,  as  do  the  pulleys, 
etc.,  of  any  pieces  of  machinery  being 
driven.  In  the  operation  of  electric  gener- 

161 


ators  for  incandescent  lighting,  the  regu- 
lating power  of  the  engine  flywheel  is  quite 
frequently  augmented  by  the  use  of  an  ad- 
ditional flywheel  on  the  armature  shaft,  oil 
a  jack-shaft  between  the  engine  and  the 
dynamo,  or  on  both  the  dynamo  shaft  and 
the  jack-shaft. 

It  is  obvious  that  the  rational  method  of 
calculating  the  energy  storing  power  re- 
quired in  the  gas-engine  flywheel  is  to 
make  a  graphical  diagram  of  the  operations 
that  take  place  within  the  engine  cylinder 
and  to  transform  them  into  a  diagram  show- 
ing the  resultant  effect  of  these  forces  upon 
the  crank-pin.  There  are  two  ways  in  which 
this  may  be  done.  One  of  these  methods 
considers  only  the  effect  of  the  pressures 
within  the  cylinder,  while  the  other  and 
most  accurate  method  brings  in  the  effect 
of  the  reciprocating  parts  of  the  engine, 
/.  ^.,  the  piston,  the  connecting-rod  and  the 
cross-head  when  it  is  employed.  Both  of 
these  methods  require  tedious  calculations, 
and  the  reader  is  referred  to  works  of  greater 
scope  than  the  present  one  for  description 
and  explanation  of  these  methods.  For  the 
case  of  a  gas  engine  operating  under  aver- 
age conditions  the  following  formulas  will 
be  found  to  give  good  results  in  practice. 
They  give  values  that  are  within  a  very  few 
percent  of  those  obtained  from  the  actual 

162 


diagram  of  the  engine,  and  show  good  re- 
sults in  practice : 
Let  W  =  the  weight  of  the  flywheel  rim  in 

pounds ; 

f=  the  diameter  of  the  flywheel  at  the 
center  of  gravity  of  the  rim  in 
inches  ; 

N=  the  r.  p.  m.  of  the  crankshaft; 
E=  the  coefficient  of  unsteadiness  per- 
missible ; 

I.  H.  P.  X  111,600,000,000 
Then  W=  f*N*R  (22> 

when  the  engine  has  an  impulse  at  every 
fourth  stroke.  If  the  I.  H.  P.  is  taken  as  the 
power  of  the  engine  when  operating  at  less 
than  the  maximum  number  of  explosions, 
the  value  of  the  figure  in  the  numerator 
must  be  increased  in  proportion.  Thus, 
should  the  calculations  be  made  for  an 
I.  H.  P.,  taken  when  the  engine  is  getting  an 
impulse  only  every  eighth  stroke,  the  weight 
found  by  the  above  formula  must  be  multi- 
plied by  2.  The  value  of  the  coefficient  E 
for  the  various  classes  of  work  is  given  by 
competent  authorities  to  be: 

For  pumping  water  and  all  ordinary 
duties 05    ; 

For  driving  machine  tools 03    ; 

For  driving  textile  machinery..    .025; 

For  driving,  dynamos 02    ; 

For  driving  spinning  machinery  .01. 

163 


164. 


If  the  flywheel  on  the  engine  is  to  be 
assisted  by  flywheels  on  a  jack-shaft,  or  on 
the  armature  shaft  of  a  dynamo  or  other 
machinery  it  may  be  driving, •  the  power 
storing  effect  should  be  divided  among  the 
various  flywheels.  This  is  done  by  first 
deciding  what  power  is  stored  by  the  fly- 
wheels on  the  engine  at  the  coefficient  of 
steadiness  employed,  and  then  finding  by 
means  of  formula  (22)  what  weight  of  fly- 
wheel is  required  on  the  jack-shaft  to  store 
the  remainder,  using  for  f  and  ^Vthe  diam- 
eter to  the  center  of  gravity  of  the  jack- 
shaft  flywheel  and  the  r.  p.  m.  of  the  jack- 
shaft. 

The  general  proportions  of  a  gas-engine 
flywheel  are  shown  in  Fig.  37.  Taking  the 
diameter  of  the  crankshaft  as  a  basis  of 
the  dimensions  of  the  hub  and  the  spokes, 
the  proportions  are  as  follows : 

h  =  ic. 

i  =  y 

d  =  .8£  to   I.2C. 

b  =  .\d  to  .$d  about.  This  dimension 
should,  however,  be  calculated  from  the 
following  formula : 


nNd* 

Wherein  B.  H.  P.  =  the  maximum  brake 
horsepower  of  the  engine ; 


! 


(23) 


165 


n  =  the  number  of  spokes ; 

N "=  the    r.  p.  in.  of  the  crank- 
shaft. 

It  appears  to  be  the  universal  practice  to 
use  six  spokes  for  a  gas-engine  flywheel. 
The  length  of  the  hub  should  be  at  least 
1.5^,  and  is  usually  from  1.75  to  2.5  times 
the  diameter  of  the  crankshaft.  The  di- 
mensions of  the  rim  must  be  made  to  suit 
the  requirements  of  the  engine.  The  width 
of  the  rim  will  depend  upon  whether  the 
engine  will  use  flywheel  as  a  pulley  or  not, 
and  upon  the  weight  required.  It  should 
be  remembered  that  the  wider  the  rim  the 
less  will  be  its  weight  for  a  given  amount 
of  energy  storage.  The  outside  diameter 
is  usually  from  four  to  five  times  the  stroke 
of  the  engine.  It  is  customary  to  limit  the 
speed  of  the  rim  to  6,000  feet  per  minute, 

or  a  maximum  diameter  of  D  =  -3 

N 

wherein  D  —  the    outside   diameter  of  the 
wheel  and  N  ^=  the  r.  p.  in. 


*  Kent's  M.  K-  1'ocketbook. 


166 


CHAPTER  XXI. 

BALANCB-WKIGHTS. 

The  proper  method  of  balancing  an  en- 
gine, and  also  the  correct  formula  for  cal- 
culating the  weight  of  the  balance-weight, 
is  a  subject  of  much  discussion  among  en- 
gineers. The  writer  finds  it  impossible  to 
attempt  to  give  what  would  be  called  aver- 
age practice  in  this  regard,  so  wide  is  the 
difference  of  opinion.  From  the  conditions 
under  which  a  gas  engine  operates,  espe- 
cially engines  with  a  single  cylinder,  it  is  not 
possible  to  balance  an  engine  perfectly  by 
means  of  a  rotating  weight.  If  the  engine 
be  balanced  for  horizontal  vibratory  effect 
it  is  found  that  it  is  too  heavily  counterbal- 
anced for  vertical  movement.  It  is  therefore 
the  custom  to  attempt  a  medium  between 
the  two.  Some  builders  balance  what  they 
consider  to  be  the  rotating  part  of  the  en- 
gine, and  make  no  allowance  for  the  recip- 
rocating parts ;  others  balance  the  rotating 
weights,  and  add  to  this  one  half  the  recip- 

167 


rocating  weight.  By  the  first  method  only 
the  crankpin,  the  crankarms  and  that  por- 
tion of  the  connecting-rod  which  is  consid- 
ered as  rotating,  is  balanced.  This  gives 
rise  to  two  sets  of  formulas,  which,  strange 
to  say,  give  apparently  good  results  in  each 
case.  The  question  now  remains,  what 
proportion  of  the  connecting-rod  should 
be  considered  as  having  a  rotating  effect  ? 
This  may  best  be  answered  by  weighing 
the  connecting-rod  in  the  following  man- 
ner :  Support  the  piston  end  of  the  rod  011 
a  trestle  or  other  convenient  support,  and 
let  it  rest  at  a  point  opposite  the  center  of 
the  bearing  on  a  knife  edge ;  support  the 
crank  end  of  the  rod  on  a  platform  or  other 
scales,  also  by  a  knife  edge,  and  see  that  the 
center  line  of  the  rod  is  horizontal.  The 
weight  of  the  crank  end  as  shown  on  the 
scale  is  that  which  should  be  taken  for  giv- 
ing rotating  effect.  If,  however,  five  eighths 
of  the  rod  be  taken  as  rotating,  the  result 
will  not  be  far  from  wrong. 

Taking  the   two   cases   cited   above,   the 
following  formulas  apply : 

Let  B  =  the  weight  of  the  balance-weight; 
M '==  the  weight   of  the  crankpin   -{- 
the  rotating  portion  of  connect- 
ing-rod ; 

K '=  weight   of    reciprocating    parts, 
including  the  remaining  portion 

168 


of  the  connecting-rod,  the  pis- 
ton and  the  piston-rod  and  cross- 
head  in  engines  that  employ 
them  ; 

J  =  weight  of  both  crankarms  ; 

m  =  crank-radius  =  one  half  the 
stroke  of  the  engine  ; 

j  =  the  distance  to  the  center  of 
gravity  of  the  crankarm  from 
the  center  of  the  crankshaft  ; 

q  =  distance  to  center  of  gravity  of 
balance-weight  from  the  center 
of  crankshaft  ; 


Then  B  —  Mm     '    ?  for  balancing  the  ro- 

q 
tating  effect  alone  ;         (24) 

(M  +  *)m  +  Jj    ,         ,    . 
And  B  =  —        :*  -  —    for     balancing 

the  rotating  weight  and  one  half 
the  reciprocating  weight.  (24  a] 
The  proper  place  for  the  balance-weight 
is  considered  by  a  great  many  designers  to 
be  undoubtedly  on  the  crankarms.  There 
are  many  builders  who  place  a  counter- 
weight on  the  flywheel  near  the  rim,  and 
some  who  core  out  the  rim  on  the  side  of 
the  flywheel  nearest  the  crankpin.  There 
are  two  advantages  for  the  latter  method; 
one  is  that  the  counterweight  may  be  much 
lighter,  and  the  other  that  it  is  cheaper  to 
make.  On  the  other  hand,  it  is  necessary 

169 


to  make  some  allowance  in  an  increase  of 
the  size  of  the  crankshaft  over  what  would 
otherwise  be  necessary,  in  order  that  it  will 
withstand  the  wrenching  effect  of  the  coun- 
terbalance when  placed  in  the  flywheel. 


170 


CHAPTER  XXII. 

FOUNDATIONS. 

Without  a  good  foundation,  an  engine 
may  be  expected  to  give  more  or  less  trouble 
by  vibration,  and  in  time  work  itself  loose 
from  such  a  foundation  as  has  been  pro- 
vided for  it.  No  engine  should  be  bolted 
directly  to  a  floor  for  anything  other  than  a 
temporary  job ;  and  even  when  the  engine 
is  to  be  placed  upon  an  upper  floor  a  foun- 
dation should  be  built  in  a  hanging  frame 
below  the  floor.  Foundations  are  usually 
built  of  either  concrete,  stone  or  brick.  On 
top  of  the  concrete  is  set  a  capstone,  the 
best  material  for  which  is  granite,  limestone, 
bluestone,  or  any  stone  of  a  close-grained 
structure  may  be  used  for  the  purpose,  but 
the  ordinary  sandstones  will  not  answer. 

Concrete  should  be  made  of  good  sand 
and  a  good  quality  of  cement  and  broken 
stone.  The  stone  should  pass  through  a 
two-inch  ring  but  not  go  through  a  one- 


.nch  ring.  Gravel,  broken  brick  and  ciii- 
iers  have  been  used,  the  latter  making  a 
tnuch  better  concrete  than  might  be  sup- 
posed. The  following  proportions  are  those 
best  for  concrete : 

Cement I  part. 

Sand 2  parts. 

Gravel  or  stone 5  parts. 

If  the  cement  is  a  good  quality  of  Port- 
land, three  parts  of  sand  may  be  used.  The 
concrete  should  be  laid  in  a  crib  in  layers 
not  over  six  inches  deep,  and  each  layer 
should  be  thoroughly  tamped  before  the 
next  is  put  in.  A  very  good  foundation 
may  be  made  cheaply  and  quickly  in  the 
following  manner:  Lay  a  brick  wall  in 
cement  mortar,  making  the  outside  bound- 
ary that  of  the  finished  foundation;  then 
fill  in  the  center  with  layers  of  brick  or 
bats,  laid  flat  as  in  a  wall,  and  loosely.  The 
intermediate  spaces  should  then  be  filled  in 
with  a  mixture  of  one  part  cement  to  one 
part  sand.  All  foundations  should  be  al- 
lowed three  days,  at  the  least,  to  set  before 
the  engine  is  put  in  place,  and  a  week  is  a 
much  better  allowance,  if  there  is  time  to 
wait  that  long.  It  is  always  best  to  start 
the  foundation  from  solid  rock  or  hard  pan 
wherever  possible,  and  it  should,  at  the 
very  least,  be  started  from  the  ground,  i 
Foundations  hung  from  an  upper  floor  or  | 

172 


built  upon  it,  should  be  placed  as  close  to  a 
wall  as  practicable.  When  building  the 
foundation,  it  is  necessary  to  insert  in  the 
concrete,  gas  pipe  of  an  internal  diameter 
equal  to  twice  the  outside  diameter  of  the 
foundation  bolts.  The  nut  or  threaded 
plate  into  which  the  foundation  bolt  screws 
is  placed  at  the  bottom  of  the  tube,  or  the 
foundation  bolt  is  set  in  with  the  tube. 
After  the  engine  is  in  place  the  tubes  should 
be  filled  with  cement.  Capstones  are  not 
necessary  with  the  smaller  engines,  and  it 
is  often  a  good  plan  to  lay  wooden  beams 
on  top  of  the  foundations,  and  to  then  put 
the  engine  on  top  of  them,  so  that  when 
the  engine  frame  is  bolted  down  it  beds 
itself  into  the  timber.  The  timber  cap 
often  stops  an  annoying  vibration  when  it 
can  be  overcome  in  no  other  way. 

In  order  to  determine  the  proper  dimen- 
sions of  an  engine  foundation  for  any  en- 
gine the  following  formula  will  be  found 
useful : 

L,et  F  =  the  weight  of  the  foundation  ; 
E  =  the  weight  of  the  engine  ; 
R  =  the  r.  p.  m.  ; 

Then  F  =  .21  E  1/~^~         (25) 

The  weight  of  brick  per  cu.  ft.  is  112  Ib, 
in  the  wall  or  foundation.  The  average 
weight  of  concrete  is  137  Ib.  per  cu.  ft.  It 
is  not  customary  to  make  any  difference  in 

173 


174 


the  foundation  design  for  the  various  ma- 
terials, and  the  author  has  found  that  the 
practice  of  many  designers  is  to  base  their 
dimensions  on  the  weight  of  concrete.  As 
a  concrete  foundation  is  %  heavier  than  a 
brick  foundation  of  the  same  size,  this  is 
evidently  an  error.  The  best  way  would 
undoubtedly  be  to  make  a  separate  drawing 
or  list  of  dimensions  for  brick,  or  to  at 
least  calculate  the  dimensions  of  the  foun- 
dation on  the  basis  of  125  Ib.  to  the  cu.  ft., 
an  average  of  the  two  weights. 

A  very  good  style  of  foundation  is  illus- 
trated in  Fig.  38.  It  is  easily  constructed 
of  any  material  by  a  fairly  good  workman. 
The  inclination  of  wall  from  the  top  to  the 
bottom  is  usually  known  as  the  batter,  and 
it  is  customary  to  make  the  batter  from  3" 
to  4X/  to  the  foot  in  height.  Instead  of 
building  the  foundation  in  tiers,  as  shown, 
some  designers  prefer  to  make  the  sides 
with  a  gradual  slope,  as  indicated  by  the 
dotted  lines.  The  number  of  foundation 
bolts  varies  from  four  to  eight,  according 
to  the  size  of  the  engine.  No  less  than  four 
bolts  are  used,  and  to  determine  roughly 
the  necessary  number  of  bolts,  divide  the 
horsepower  of  the  engine  by  6,  always  using 
an  even  number.  The  sizes  of  the  bolts  to 
use,  may  be  determined  approximately  as 
follows : 


Let  //=  the  horsepower  of  the  engine  ; 
y  =  the  area  of  one  bolt  ; 
k  =  the  number  of  bolts  ; 
(26) 


_ 

k 

It  should  be  observed  that  this  formula 
is  entirely  an  empirical  one,  and  that  the 
designer  should  consider  the  strain  upon 
the  bolt  that  is  farthest  from  a  line  directly 
under  the  crankshaft,  in  cases  wherein  the 
shaft  is  at  an  unusual  distance  from  the  top 
of  the  foundation.  As  a  rule  it  will  be 
found  that  the  above  formula  gives  bolts  of 
ample  size  for  engines  of  the  usual  design. 

In  case  it  is  necessary  to  go  very  deep  to 
find  a  solid  bottom  on  which  to  set  the 
foundation,  piles  may  be  driven  over  an 
area  slightly  larger  than  that  taken  up  by 
the  base  of  the  regular  foundation,  or  a 
crib  of  timbers  laid  in.  A  sub-foundation 
of  timber  or  piles  should  be  laid,  if  pos- 
sible, at  a  sufficient  depth  to  keep  the  tim- 
ber covered  with  water  or  very  damp  earth. 


CHAPTER  XXIII. 

MISCELLANEOUS    FORMULAS. 

The  following  formulas  may  prove  them- 
selves useful  to  those  who  design  or  handle 
gas  engines  : 

For  the  diameter  of  the  camshaft : 

Let  c  =  the  diameter  of  the  camshaft ; 
D  =  the    diameter   of    the   cylinder 

in  inches  ; 

Then  c  =  .057  D  -|-  .625. 
For  the  volume  of  the  muffler ; 

Let  M  =  the  volume  of  the  muffler  in 

cu.  in. ; 
L  =  the   length   of  the  stroke  in 

inches ; 

Then^/=  3.5 />£. 

For  a  closed  circulating  system  of  cooling 
the  cylinder  the  capacity  of  the  tanks  is 
made  from  20  to  50  gallons  per  I.  H.  P. 
Thirty  gallons  is  usually  considered  an 
ample  allowance.  The  allowance  for  evap- 
oration is  o.i  gallon  per  D.  H.  P.  per  hour. 
For  water  flowing  through  the  jacket  Mr. 

177 


Frederick  Grover  recommends  4^  gallons 
per  I.  H.  P.  per  hour. 

The  proper  size  of  marine  engine  to  use 
for  launches  up  to  50  ft.  long  may  be  roughly 
estimated  by  means  of  the  following  equa- 
tion : 

Let  JB=  the  length  of  the  boat  on  the 

load  waterline  in  feet ; 
H  =  the  horsepower  of  the  engine  ; 

Then  H=*  f  —  9. 

For  the  smaller  craft,  to  which  so  many 
gasoline  engines  are  applied,  the  usual  rules 
for  the  diameter  and  pitch  of  a  screw  pro- 
peller do  not  seem  to  be  applicable.  The 
author  has  derived  the  following  empirical 
formula  for  pleasure  boats  which  use  en- 
gines of  from  i  to  12  horsepower. 

Let  d  =  the  diameter  of  the  propeller 

in  inches ; 

H  =  the  horsepower  of  the  engine  ; 
R  =  the  r.  p.  in. ; 

Then  for  a  3-bladed  propeller  with  pitch 
and  diameter  equal, 

rf=  V22-S2SL2+  164 
R 

For  a  2-bladed  propeller  the  diameter 
should  be  about  8%  greater  than  for  the 
3-bladed  propeller.  It  may  be  a  new  propo- 
sition to  many  to  make  the  pitch  and  the 
diameter  equal,  as  it  is  the  custom  of  a 


great  many  boat  builders  to  make  the  pitch 
1.3  d.  One  of  the  most  successful  launch 
builders  in  this  country  uses  the  ratio 
pitch  =  diameter,  and  speeds  his  engines 
up  to  correspond. 


179 


CHAPTER  XXIV. 

TESTING. 

Hvery  manufacturer  of  gas  engines  has 
a  department  known  as  the  testing  floor, 
equipped  more  or  less  fully  with  apparatus 
for  determining,  before  the  engine  leaves 
the  factory,  if  it  is  working  satisfactorily. 
The  primary  objects  of  the  test  are,  first,  to 
find  out  if  the  governor  is  so  set  as  to  give 
the  engine  its  proper  speed;  second,  by 
means  of  the  indicator,  to  discover  if  the 
igniter  is  properly  timed,  whether  or  not 
the  valves  open  at  the  proper  points  in  the 
cycle,  and  to  see  if  the  compression  is  of 
the  right  amount.  The  gas-engine  indica- 
tor diagram  is  of  value  for  the  determination 
of  other  points  in  the  working  of  the  engine, 
as  has  been  discussed  in  Chapter  XIV.  The 
third  object  of  the  test  is  to  determine  if 
the  engine  is  giving  the  required  amount  of 
horsepower  at  the  pulley.  This  is  known 
as  the  delivered  or  brake  horsepower,  de- 
noted bv  either  the  letters  D.  H.  P.  or  B.  H.  P. 

180 


It  is  determined  by  means  of  a  form  of  ab- 
sorption dynamometer  known  as  the  prony 
brake.  The  fourth  object  of  the  test  is  the 
determination  of  the  fuel  consumption  of 
the  engine  per  I.  H.  P.  per  hour. 

The  necessary  apparatus  for  a  gas-engine 
test,  as  it  is  usually  carried  out  on  the  test- 
ing floor,  is  as  follows  :  A  good  steam-engine 
indicator,  with  a  piston  having  an  area  of 
X  square  inch,  and,  if  possible,  a  pencil 
movement  of  extra  strength,  is  the  princi- 
pal requisite  for  determining  the  I.  H.  P. 

There  are  indicators  now  to  be  had  that 
are  designed  expressly  for  the  gas  engine 
and  with  the  above  features.  There  should 
also  be  some  good  type  of  reducing  motion 
in  order  that  the  movements  of  the  stroke 
of  the  piston  may  be  reduced  to  a  stroke  of 
between  2^x/  and  3^",  which  is  the  usual 
length  of  the  indicator  diagram.  There 
should  be,  if  it  is  possible  to  obtain  it,  a  test 
meter  reading  in  single  cubic  feet  in  order 
that  the  fuel  consumption,  when  the  gas 
engine  is  used,  can  be  measured  with  some 
degree  of  accuracy.  There  should  also  be 
a  prony  brake  large  enough  to  be  attached 
to  a  pulley  of  considerable  diameter.  The 
brake  should  have  some  means  by  which  its 
grip  upon  the  wheel  may  be  quickly  al- 
tered, and  there  should  also  be  a  platform 
fe,  and  the  scale  should  be  accurately 
181 


tested  beforehand  with  a  standard  weight  to 
determine  if  its  readings  are  correct.  The 
experimenter  should  be  supplied  with  a 
good  form  of  revolution  or  speed  counter, 
those  being  the  best  which  have  a  soft  rub- 
ber tip  for  placing  in  the  center  countersink 
at  the  end  of  the  crankshaft. 

For  a  more  refined  test  than  is  usual  on 
the  testing  floor  of  a  factory  there  is  needed 
a  means  of  measuring  the  jacket  water, 
thermometers  for  taking  the  temperature  of 
the  water  before  passing  into  the  jacket  and 
as  it  is  leaving,  a  pyrometer  for  determin- 
ing the  temperature  of  the  exhaust  gases, 
a  pressure  gauge  or  a  manometer  for  de- 
termining the -pressure  of  the  gas,  a  ther- 
mometer for  determining  the  temperature  of 
the  same,  a  thermometer  to  be  hung  on  the 
wall  near  the  engine  to  determine  the  tem- 
perature of  the  room,  and  a  barometer  for 
measuring  the  pressure  of  the  atmosphere 
at  the  time  the  test  is  made.  This  appa- 
ratus is  necessary  only  if  making  the  test 
for  discovery  of  faults  in  design,  and  when 
it  is  desired  to  obtain  data  upon  which  to 
make  improvements  in  the  engine.  It 
would,  however,  be  a  good  plan  to  always 
take  the  pressure  of  the  gas,  particularly 
when  natural  gas  is  used  and  the  pressure 
is  more  than  a  few  ounces  per  square  inch. 
Otherwise  the  experimenter  mav  be  led  into 

182 


grave  errors  by  striving  to  calculate  the  fuel 
consumption  of  his  engine.  No  gas  engine 
should  ever  leave  the  factory  without  hav- 
ing undergone  a  test  for  speed  and  for  de- 
livered horsepower,  nor  without  several 
indicator  diagrams  having  been  taken  from 
the  engine. 

A  gas  engine  rigged  up  for  the  purpose 
of  making  a  thorough  test  is  shown  in  Fig. 
39.  The  prony  brake  is  shown  applied  to 
the  flywheel,  and  the  engine  is  running 
over,  as  shown  by  the  arrow.  The  brake 
consists  of  the  strap  a  with  the  blocks  b 
bearing  upon  the  periphery  of  the  wheel, 
and  the  brake-arm  made  of  the  two  boards 
ff.  Two  cast-iron  or  wrought-iron  angles 
cc  are  placed  where  the  band  is  parted,  and 
through  them  is  put  the  bolt  d>  used  to 
tighten  the  brake  by  means  of  the  threaded 
crank  e.  A  platform  scale  is  placed  at  /£, 
and  the  thrust  of  the  brake  is  applied  to 
the  scale  by  the  arm  f  acting  through  the 
knife  edge  g,  the  iron  block  h  and  the 
wooden  stand  j.  The  distance  L  from  the 
center  of  the  crankshaft  to  the  point  where 
the  knife  edge  rests  upon  the  block  h  is 
known  as  the  length  of  the  lever  arm. 

The  indicator  is  shown  at  z,  the  cord  from 
the  indicator  passing  to  the  smaller  drum 
of  a  reducing  wheel  r,  and  a  cord  from  the 
larger  wheel  being  attached  to  the  piston. 

i 


184 


as  shown  in  the  small  sketch  at  the  upper 
right-hand  corner  of  the  figure.  To  attach 
the  cord  to  the  piston  a  piece  of  ^x/  round 
iron  is  bent  into  the  shape  illustrated  and 
flattened  at  the  end  opposite  the  eye  m. 
Through  the  flattened  portion  two  holes 
are  drilled,  and  the  rod  is  fastened  to  the 
inside  of  the  piston  by  means  of  machine 
screws  or  capbolts. 

Water  enters  the  water-jacket  through 
the  pipe  ze/,  controlled  by  the  valve  z>,  and 
it  leaves  the  jacket  through  the  pipe  w. 
Thermometers  are  placed  at  t  and  t  to  de- 
termine the  temperature  of  the  water  as  it 
enters  and  as  it  leaves  the  jacket.  These 
thermometers  do  not  set  directly  in  the 
water  but  are  in  small  cups  filled  with  oil. 

In  leaving  the  jacket  the  water  is  caught 
in  the  box  B  and  either  weighed  or  meas- 
ured as  is  most  convenient.  In  case  it  is 
desired  to  weigh  the  water,  two  receptacles 
should  be  provided  and  one  emptied  while 
the  other  is  being  filled.  Catching  the 
weight  "on  the  fly"  is  not  an  accurate  meth- 
od and  should  be  avoided.  When  using  two 
receptacles,  the  stream  of  water  should  be 
changed  just  at  the  time  the  signal  is  given 
for  taking  the  reading. 

When  it  is  desired  to  measure  the  water 
by  volume,  the  receptacle  may  be  made  in 
the  form  of  a  box  of  the  following  dimen- 

185 


sions,  in  order  to  make  the  measurement 
easier  to  read.  If  the  dimensions  of  the 
tank  are  37^  x  37^-  inches,  and  the  meas- 
uring stick  s  is  marked  off  in  half-inch 
divisions,  each  j^-inch  in  depth  will  indi- 
cate 25  Ib.  of  water.  If  a  smaller  tank  is 
desired,  it  maybe  made  26^  x  26$  and  each 
inch  in  depth  will  indicate  approximately  25 
Ib.  of  water.  These  measurements  are  made 
for  water  at  a  temperature  of  150°  F.,  which 
is  about  the  average  temperature  of  the 
water  leaving  the  water-jacket.  For  very 
accurate  determinations  the  water  should, 
of  course,  be  weighed.  Weighing  or  meas- 
uring the  water  is  necessary  when  making 
a  thorough  test,  in  order  to  find  the  amount 
of  heat  carried  off  in  the  water. 

A  meter  is  shown  on  the  wall  at  M  with 
the  gas  bag  at  G.  On  the  wall  near  the  gas 
bag,  hangs  the  thermometer  T  for  determin- 
ing the  temperature  of  the  atmosphere  and 
a  barometer  X  for  determining  the  atmos- 
pheric pressure.  The  temperature  of  the 
exhaust  gases,  as  they  leave  the  engine,  is 
measured  by  means  of  the  pyrometer  p. 
The  temperature  of  the  gas  is  taken  just 
before  it  enters  the  meter,  by  the  thermom- 
eter t" ',  and  its  pressure  by  means  of  the 
manometer  m' .  It  is  also  advisable  to  use  a 
meter  for  the  measurement  of  the  air  when 
it  is  necessary  to  compute  the  ratios  of  the 

1 86 


fuel  to  the  air  under  the  various  conditions. 
It  has  been  the  custom  in  many  testing 
rooms  to  compute  the  volume  of  the  air 
from  the  difference  between  the  quantity  of 
gas  entering  the  cylinder  at  each  working 
stroke  and  the  volume  of  the  piston  dis- 
placement. Such  a  method  is  an  erronous 
one,  as  there  is  usually  more  or  less  wire- 
drawing, and  a  certain  quantity  of  the  prod- 
ucts of  combustion  remains  from  the  pre- 
vious charge,  hence  the  air  should  be  meas- 
ured by  a  meter. 

In  order  that  the  reader  may  thoroughly 
understand  the  method  of  making  a  com- 
plete test  and  of  working  up  the  data,  it  will 
be  explained  in  its  entirety.  In  ordinary 
testing  he  may  select  such  portions  of  the 
complete  test  as  will  suit  his  purpose,  and, 
before  starting  the  test,  a  log  should  be 
made  out  as  shown  on  page  188.  This  log 
shows  at  the  head  of  each  column  just  what 
readings  should  be  taken.  The  last  three 
columns  are  for  convenience  when  working 
up  the  data  after  the  test,  while  the  balance 
of  the  log  is  for  data  taken  while  the  test  is 
in  progress. 

In  making  the  test,  particularly  when  a 
large  number  of  readings  are  to  be  taken, 
the  engineer  in  charge  should  have  a  suffi- 
cient number  of  assistants,  in  order  that  the 
readings  may  be  taken  immediately  after 

187 


S  I 


'd  'H  'I 


•I81-BAY  JOS8 

-qoni  'a 


•njoAai  .lad 
spuuod-^oo^ 


•spnnod 


•spnnod 


u  aad  'Aa>[ 


1  88 


the  signal.  One  man  should  be  posted  at 
the  brake  to  keep  the  pressure  upon  the 
scale  as  nearly  as  possible  at  the  same  point 
during  one  run.  Another  man  should  have 
charge  of  the  indicator,  and  a  third  should 
read  temperatures,  measure  the  water,  and 
take  the  readings  of  the  two  meters  and  the 
barometer.  This  gives  the  third  man  the 
greatest  part  of  the  work,  and  a  fourth  man 
could  therefore  be  used  to  advantage.  The 
man  in  charge  of  the  indicator  may  also 
take  the  speed  of  the  engine  and  count  the 
number  of  explosions  per  minute.  For 
taking  the  speed  of  the  engine,  a  continuous 
counter  will  be  found  more  convenient  than 
an  ordinary  speed  counter,  as  the  speed  can 
be  taken  in  less  time.  When  there  are  but 
two  observers,  readings  should  be  taken  at 
intervals  of  ten  minutes,  and  the  man  in 
charge  of  the  indicator  should  take  all  read- 
ings, as  the  brake  requires  constant  atten- 
tion. 

The  test  should  be  divided  into  runs, 
each  run  being  made  at  the  same  horse- 
power throughout.  One  run  should  be 
made  at  the  full  power  of  the  engine, 
another  at  the  rated  horsepower,  and  a 
third  at  110  load  with  the  brake  off.  The 
number  of  runs,  at  horsepowers  other  than 
the  above,  will  depend  upon  the  size  of  the 
engine  and  the  time  at  the  disposal  of  the 

189 


experimenter.  The  author  would  suggest 
making  a  run  at  quarter  load,  half  load,  and 
three-quarter  load  as  well  as  at  the  loads 
already  noted.  At  least  ten  readings  should 
be  taken  during  each  run,  and  fifteen  or 
twenty  readings  would  be  much  better,  if 
accurate  results  are  desired. 

The  test  should,  if  possible,  be  in  charge 
of  a  competent  engineer.  He  should  be 
provided  with  a  whistle  which  should  be 
blown  as  a  preparatory  signal  thirty  seconds 
before  the  time  of  taking  the  reading.  Two 
blasts  of  the  whistle  should  be  the  prepara- 
tory signal  and  one  blast  should  be  the 
signal  for  taking  the  readings.  Promptness 
should  be  observed,  each  man  taking  his 
post  at  the  preparatory  signal.  Under  no 
circumstances  should  an  outsider  be  allowed 
to  interfere,  and,  above  all,  no  one  but  an 
observer  engaged  upon  the  test  should  be 
permitted  to  take  a  reading.  Always  enter 
the  data  upon  the  regular  log.  Keeping 
notes  upon  loose  slips  of  paper  leads  to 
confusion,  and  it  should  be  avoided. 

At  some  convenient  time,  either  before  or 
after  the  test,  the  diameter  of  the  piston, 
the  length  of  the  stroke,  and  the  clearance 
should  be  carefully  measured.  In  order  to 
measure  the  clearance,  the  crank  should  be 
placed  exactly  upon  its  inner  dead  center 
and  the  valves  firmly  seated.  Carefully 

190 


^  weigh  a  quantity  of  water  and  fill  the  com- 
pression space  so  that  it  is  just  full  and  no 
more,  being  careful  to  spill  none  of  the 
water.  Then  weigh  the  remaining  water 
and  the  difference  between  the  two  weights 
will  be  the  quantity  necessary  to  fill  the 
compression  space.  Water  at  39.1°  F.  weighs 
62.5  Ib.  per  cu.  ft.  and  dividing  the  weight 
of  the  water  taken  to  fill  the  compression 
space,  by  62.5  gives  the  volume  in  cu.  ft.  If 
the  water  is  much  warmer  than  39.1°,  the 
weight  may  be  found  by  the  following 
formula : 

62'5  X  2 =  Wt.percu.  ft.  , 

/  +  461,       500  f3i 

•* 


500  t  -\-  461 

Wherein  t  =  the  temperature  of  the  water. 

This  formula  gives  a  close  approximation 
to  the  correct  weight.  For  the  usual  hy- 
drant temperatures,  dividing  by  62.5  gives 
results  sufficiently  close  for  the  purpose. 

In  making  up  a  report  of  the  test,  the 
form  shown  on  page  192  will  be  found  con- 
venient. The  first  line  should  be  filled  in 
with  the  name  of  the  engine  and  the 
manufacturer,  the  second  line  with  the 
name  of  the  party  by  whom  the  test  is 
made  or  the  engineering  firm  of  which  he 
is  the  representative,  and  the  third  line  by 
the  locality  at  which  the  test  is  made,  to- 
gether with  the  date. 

191 


REPORT  OK  TEST. 

(las  Engine 

Test  made  by 

At...  ..19.. 


DIMENSIONS  OF  ENGINE. 

Diameter  of  piston In. 

Area  of  piston Sq.  in. 

Length  of  stroke Ft. 

Piston  displacement Cu.  ft. 

Clearance Cu.  ft. 

Clearance.  .  .  Per  cent. 


DATA. 

Duration  trial.    . Hrs. 

Gas  per  hour Cu.   ft. 

Air  per  hour .Cu.  ft. I 

Ratio,  gas  to  air 

Jacket-water  per  hour. T/b.j 

Jacket-water  temperature,  inlet I 

Jacket- water  temperature,  outlet i 

Jacket-water  temperature,  range.  .  F.cj 
Revolutions  per  minute  .  .  .  .Average. 

Revolutions  per  hour 

Explosions  per  minute Average 

Explosions  per  hour 

Temperature  exhaust F.c 

Temperature  room F.c 


192 


Length  of  lever  arm Ft, 

Brake  load,  average Lb, 

Gas — Weight  of  cubic  foot Lb, 

Air — Weight  of  cubic  foot Lb 

Mixture— Weight  of  cubic  foot.  .  .Lb 

Specific  heat,  gas 

Specific  heat,  air 

Specific  heat,  mixture 

Heat  value  cu.  ft.  gas B.  T.  U 

RESULTS. 

Work — Ft.  Ib.  per  ruin Average, 

WTork — Ft.  Ib.  per  hour Average 

D.  H.  P Average 

Indicated  M.  B.  P Average, 

Indicated  H.  P Average 

Gas  per  I.  H.  P Cu.  ft 

Gas  per  D.  H.  P Cu.  ft 

Mech.  Eff.  D.,  H.  P.  -:-  I.  II.  P 

Friction  Loss  I.  H.  P.— D.  H.  P      

HEAT  PER  HOUR. 

Supplied  by  gas B.  T.  U 

Absorbed  by  jacket-water.  .  .  .B.  T.  U 

Exhausted B.  T.  U 

Absorbed  in  work B.  T.  U 

Radiation B.  T.  U: 

Thermal  efficiency Percent 

B.  T.  U.  per  I.  H.  P ' 


A  great  many  of  the  items  in  the  report 
need  no  explanation,  and  only  those  that 
are  not  likely  to  be  understood  by  the 
reader  will  be  explained.  The  percentage 
of  clearance  is  found  by  dividing  the  vol- 
ume of  the  clearance  by  the  piston  dis- 
placement. The  ratio  of  the  gas  to  the  air 
is  the  quantity  of  gas  used  per  hour  divided 
by  the  quantity  of  air.  In  engines  which 
take  air  into  the  cylinder  at  each  cycle 
whether  gas  enters  or  not,  the  ratio  may  be 
obtained  only  when  the  engine  runs  with- 
out missing  an  explosion.  The  range  of 
temperature  for  the  jacket  water  is  the 
difference  between  the  temperatures  of  the 
outlet  and  the  inlet  water.  The  weight  of 
the  gas  may  be  obtained  from  the  gas  com- 
pany or  it  may  be  computed  from  the 
results  of  an  analysis  of  the  gas  by  multi- 
plying the  weight  of  a  cubic  foot  of  each 
constituent  by  the  percent  contained  in  the 
gas  and  adding  the  results.  The  following 
table  gives  the  weights  per  cu.  ft.  of  those 
gases  which  occur  most  frequently  and  in 
the  greatest  quantities  in  gases  used  for  gas 
engines,  together  with  their  specific  heat 
at  constant  volume. 


194 


L,b.  per        Spec, 
Cu.  Ft.        Heat 

0447  .470 

Olefines 1174  -332 

Hydrogen o°559  2.406 

Carbon  monoxide 0783  .173 

Nitrogen 0783  .173 

Carbon  dioxide 1060  .171 

Oxygen 1060  .155 

These  weights  are  for  the  gases  when  at 
an  atmospheric  pressure  of  14.7  Ib.  per  sq. 
in.  and  a  temperature  of  32°  F.  The  spe- 
cific heat  of  a  mixture  may  be  found  in  the 
same  manner  as  the  weight,  by  multiplying 
the  specific  heat  for  each  gas  by  the  percent 
contained  in  the  fuel  and  adding  the  results. 
The  weight  of  air  at  32°  F.  and  at  a  pres- 
sure of  14.7  Ib.  per  sq.  in.  is  .08082  Ib.  The 
specific  heat  of  air  at  constant  volume  is 
.1688.  The  weight  of  a  cu.  ft.  of  the  mix- 
ture may  be  found  by  multiplying  the 
weight  of  the  gas  as  already  found  by  the 
percent  of  gas  in  the  mixture,  and  then 
multiplying  the  weight  of  air  per  cu.  ft.  by 
the  percent  in  the  mixture.  The  sum  of 
these  two  results  will  be  the  weight  of  the 
mixture.  The  heat  value  of  the  gas  should 
in  every  case  be  determined  at  a  laboratory. 
When  it  is  necessary  to  know  the  heat  value 
a  sample  of  the  gas  should  be  sent  to  a  lab- 
oratory for  examination,  taking  samples  of 

195 


the  gas  at  various  times  and  mixing  them 
to  obtain  an  average.  The  heat  values  of 
various  fuels  will  be  found  in  Table  I  ;  but 
gas  is  an  uncertain  quantity  in  this  respect, 
and  the  table  is  not  to  be  relied  upon  when 
accurate  results  are  desired. 

Always,  when  making  a  gas-engine  test, 
the  volumes  of  the  gases,  both  air  and  fuel, 
should  be  reduced  to  a  standard  tempera- 
ture and  atmospheric  pressure  for  the  pur- 
pose of  comparison.  It  has  long  been  the 
custom  of  engineers  to  use  as  standard/. 
the  temperature  of  freezing  water  and  tlit 
average  pressure  of  the  atmosphere  at  the 
sea  level,  or  30"  of  mercury.  To  reduce 
the  gas  from  the  volume  at  which  the  tesc 
is  made  to  its  corresponding  volume  at  32" 
and  at  30"  of  mercury  in  the  barometer, 
the  following  formula  should  be  used: 
Let  7^=  the  temperature  at  the  time  of 

the  test  ; 
/=  the  pressure  in  inches  of  mer- 

cury ; 
i1     --  the  volume  at  this  pressure  and 

temperature; 
/         the  volume  at  30"  of  mercury 

and  at  32°  P. 
Then  for  air  : 


30  x  (1  -1-461  ) 
This  formula  will  also  give  a  sufficiently 

10 


close  approximation  when  used  for  gas. 
The  pressure  by  barometric  measure  has 
been  used  in  this  formula,  as  more  conven- 
ient than  the  ordinary  method  of  comput- 
ing on  the  basis  of  pressure  in  Ib.  per  sq.  in. 
In  order  to  reduce  the  pressure  of  the  gas, 
when  measured  in  inches  of  water,  to  an 
equivalent  pressure  in  inches  of  mercury, 
divide  the  pressure  in  inches  of  water  by 
13.62.  If  the  pressure  of  the  gas  is  meas- 
ured in  Ib.  per  sq.  in.,  multiply  this  pres- 
sure by  2.033  to  reduce  to  inches  of  mercury. 
These  ratios  are  for  temperatures  of  32°  F., 
and  will  be  found  sufficiently  accurate  for 
ordinary  temperatures  without  temperature 
corrections. 

The  work  in  foot  pounds  per  minute  is 
computed  from  the  indicator  diagram.  It 
is  the  continued  product  of  the  M.  B.  P., 
the  area  of  the  cylinder  in  sq.  in.,  the  length 
of  the  stroke  in  feet  and  the  number  of 
explosions  per  minute.  The  quantity  of 
heat  supplied  by  the  gas  per  hour  is  the 
product  of  the  heat  value  of  the  gas  per  cu. 
ft.  by  the  number  of  cu.  ft.  used  per  hour. 
The  heat  absorbed  by  the  jacket  water  is 
the  product  of  the  temperature  range  by 
the  weight  of  the  water  supplied.  The  heat 
absorbed  in  work  is  the  number  of  ft.  Ib. 
per  hour  divided  by  the  number  778,  as  778 
ft.  Ib.  is  the  equivalent  of  a  B.  T.  U.  (British 

197 


thermal  unit).  A  British  thermal  unit  is 
the  quantity  of  heat  necessary  to  raise  one 
pound  of  water  through  a  temperature  of 
one  degree  Fahrenheit.  The  heat  carried 
off  by  the  exhaust  gases  is  found  by  the 
formula  given  below : 

Let  S  =  the  specific  heat  of  the  mixture  ; 
w  =  the  weight  of  i  cu.  ft.  of  the  mix- 
ture in  pounds ; 
q  =  the  quantity  of  the  mixture  in 

cu.  ft.  exhausted  per  hour ; 

T  =  the  temperature  of  the  room  or 

the  average  temperature  of  the 

air  and  gas  entering  the  engine  ; 

T'  =  temperature    of  the  exhaust   as 

measured  by  the  pyrometer ; 
U  =  the  quantity  of  heat  carried  off 

by  the  exhaust  in  one  hour. 
Then  U  —  Swq  (  T—  T  i.         (33 ) 
The    volume    of    the    mixture     passing 
through  the  exhaust,  is  the  sum  of  the  gas 
and  the  air  used  by  the  engine,  and  it  in- 
cludes all  air  passing  through  the  exhaust 
for  any  reason. 

The  heat  otherwise  unaccounted  for,  and 
determined  by  subtracting  the  above  three 
results  from  the  heat  supplied  by  the  gas, 
is  usually  credited  to  loss  by  radiation.  To 
be  strictly  accurate,  the  quantity  of  un- 
burned  fuel  passing  through  the  exhaust 
should  be  determined,  and  the  heat  value 

198 


)f  this  waste  fuel  subtracted  from  that  sup- 
plied by  the  fuel  taken  into  the  engine.  • 

The  thermal  efficiency  is  the  quotient  of 
';he  heat  absorbed  in  work  divided  by  the 
heat  supplied  to  the  engine  in  the  fuel.  It 
is  usually  written  as  a  percentage,  and  it  is 
the  only  basis  upon  which  two  engines 
should  be  compared  for  efficiency. 

The  indicated  horsepower  of  a  gas  engine 
is  determined  from  the  indicator  diagram. 
The  area  of  the  diagram  should  first  be 
found  by  means  of  planimeter.* 

The  M.  E.  P.  is  determined  by  multiplying 
the  mean  ordinate  by  the  scale  of  the  indi- 
cator spring.  In  indicators  using  a  special 
piston  for  indicating  the  gas  engine,  with 
an  area  of  the  spring  of  X  sq.  in.,  the  scale 
of  the  spring  must  be  multiplied  by  two  for 
the  scale  of  the  diagram,  unless  it  is  ex- 
pressly marked  for  the  smaller  piston. 

To  find  the  I.  H.  P.,  when  the  M.  E.  P.  is 
known,  the  following  formula  should  be 
used : 


*For  the  method  of  using  the  planimeter  the 
reader  is  referred  to  works  upon  that  subject,  as 
space  will  not  permit  of  its  treatment  in  this  vol- 
ume. The  area  of  the  diagram  should  then  be 
divided  by  its  length,  and  the  result  will  be  the 
mean  ordinate. 


199 


/  H.  P.  L        (34) 

33,OOO 

Wherein  P  =  the  M.  E.  P. ; 

/       the  length  of  the  stroke  in 

feet; 
a  =  the  area   of  the  piston   in 

sq.  in. ; 
n  =  the  number  of  explosions 

per  minute. 

The  reader  should  observe  the  difference 
between  the  value  of  n  in  this  formula  and 
value  of  the  same  letter  in  the  similar  for- 
mula for  steam  engines.  In  the  formula 
for  the  steam  engine,  n  is  the  symbol  for 
the  number  of  revolutions  per  minute. 

To  find  the  D.  H.  P.  of  the  engine,  the 
length  of  the  brakearm— L,  Fig.  39 — the 
r.  p.  m.  and  the  pressure  exerted  upon  the 
scale  must  be  known.  The  formula  for  the 
D.  H.  P.  is  : 

D.  H.  P.  =  .0001904  pin         (35). 
Wherein  p  =  the  pressure  upon  the  scale 

(net)  ; 

/  =  the  length  of  the  brakearm  ; 
;/  =  the  r.  p.  in. 

The  net  pressure  upon  the  scale  should 
be  found  by  subtracting  the  pressure  ex- 
erted upon  the  scale  by  the  unbalanced 
portion  of  the  brakearm  and  the  weight  of 
the  block  /,  Fig.  39,  from  the  total  pressure 
exerted  upon  the  scale.  In  order  to  find 


the  effect  of  the  unbalanced  portion  of  the 
brakearm,  proceed  in  the  following  man- 
ner :  When  the  engine  is  not  running,  have 
a  man  stand  upon  the  scale  platform  and 
balance  his  weight,  i.  e.,  weigh  him.  Now 
balance  the  scale  when  he  has  hold  of  the 
brakearm  and  is  pulling  upward  against  a 
slight  friction  on  the  brakewheel  or  pulley, 
and  again  when  the  man  is  pushing  down 
on  the  arm.  The  brakearm  should  be 
grasped  close  by  the  knife  edge  and  the 
scale  balanced  when  the  brake  is  in  motion. 
Add  together  the  weight  on  the  scale  when 
the  brakearm  is  being  pulled  up  and  the 
weight  when  it  is  being  pushed  down,  and 
subtract  the  weight  of  the  man  from  half  this 
sum.  The  result  will  be  the  pressure  due 
to  the  unbalanced  portion  of  the  arm.  Thus, 
suppose  the  man  to  weigh  160  Ib.  and  that 
when  the  arm  is  being  pulled  up  the  scale 
balances  at  180  Ib.,  while  when  the  arm  is 
being  pushed  down,  the  scale  balances  at 
170  Ib.,  the  effect  of  the  arm  would  be : 

'7°-'-l8o_i6o  =  i5lb. 

2 

When  making  a  brake  test  the  man  in 
charge  of  the  brake  should  keep  constant 
watch  of  the  scale  beam,  with  his  hand 
always  on  the  lever  e,  Fig.  39.  Owing  to 
the  wide  fluctuations  in  pressure  upon  the 
piston  of  a  gas  engine,  especially  in  a  hit- 


and-miss  engine,  this  is  no  easy  task,  and  a 
good  man  should  be  selected  for  this  post. 
The  scale  beam  should  be  kept  floating  at 
all  times,  otherwise  all  the  computations 
for  D.  H.  P.  will  have  no  good  foundation. 
When  making  a  brake  test  of  any  duration, 
or  when  the  engine  is  a  large  one,  running 
water  should  be  kept  on  the  band  while  the 
engine  is  going. 

On  the  factory  testing  floor,  it  is  not  cus- 
tomary to  do  any  more  than  take  the  D.  H. 
P.,  the  I.  H.  P.  and  the  fuel  consumption. 
Sometimes  a  brake  test  only  is  made.  It  is 
always  best,  however,  to  take  a  sufficient 
number  of  indicator  diagrams  to  determine 
if  the  ignition  is  properly  timed  and  if 
there  is  any  derangement  of  the  valves. 


CHAPTER  XXV. 

SELECTION. 

In  selecting  a  gas  engine  beware,  first  of 
all,  of  the  oily  tongue  of  the  salesman. 
Every  gas-engine  manufacturer  makes  the 
•'  best  gas  engine  on  earth."  Yet  the  mar- 
ket is  overstocked  with  poor  gas  engines. 
To  find  out  what  gas  engine  is  best  adapted 
to  your  special  line  of  work,  consult  several 
users  of  gas  engines  who  are  employing  the 
engines  for  the  same  class  of  machinery 
which  you  intend  to  drive.  The  engine 
that  will  give  satisfactory  service  pumping 
water  may  be  a  good  engine  for  running 
an  electric  light  plant,  but  it  is  doubtful  if 
the  regulation  is  sufficiently  close  for  the 
purpose.  On  the  other  hand,  the  engine 
having  heavy  flywheels  and  a  sensitive 
governing  device,  built  expressly  to  meet 
the  rigid  requirements  of  an  electric  lighting 
service,  is  too  costly  a  machine  to  be  pur- 
chased for  pumping  water,  because  a  cheaper 
engine  will  answer  the  purpose  just  as  well, 


and  the  difference  may  be  placed  in  the 
owner's  pocket. 

When  you  go  to  consult  your  neighbor 
with  reference  to  his  engine  be  prepared 
with  questions  regarding  the  operation  of 
the  engine,  and  also  make  it  a  point  to  see 
the  engine  in  operation  and  watch  it  at 
work.  Then  find  out  as  nearly  as  possible 
how  much  the  engine  costs  the  owner  for 
repairs,  and  how  often  and  for  how  long  the 
engine  has  been  laid  up  for  repairs.  Deter- 
mine the  time  since  the  engine  left  the  fac- 
tory, and  whether  it  has  been  in  constant 
service  ever  since  that  time.  If  the  engine  is 
in  a  filthy  condition,  or  if  it  is  running  with 
its  parts  out  of  joint  when  it  is  apparent 
that  they  could  just  as  well  be  adjusted  to 
run  properly,  score  a  few  points  in  favor  of 
the  engine  and  against  the  engineer.  An 
engine  that  will  do  fairly  good  work  under 
bad  management  has  something  to  recom- 
mend it.  If,  however,  the  engine  is  clean 
and  all  possible  adjustments  made,  and  yet 
is  running  in  a  noisy,  jerky  way,  score  a 
point  against  it. 

If  the  engine  is  counterbalanced  with  the 
counterweights  in  the  flywheel,  stand  in  a 
position  in  line  with  the  axis  of  the  cylin- 
der and  observe  if  the  flywheel  is  running 
true  at  the  side.  If  it  sways  back  and  forth 
it  is  a  sign  that  the  crankshaft  is  not  strong 

204 


enough  to  withstand  the  strain  produced 
by  the  counterweight.  Determine  if  the 
bearings  give  much  trouble  from  overheat- 
ing, especially  when  the  engine  is  working 
under  full  load.  Ask  if  the'  igniter  mechan- 
ism gives  much  trouble,  and  if  frequent  re- 
newals of  its  various  parts  are  necessary. 
In  fact,  the  necessity  for  the  frequent  re- 
newal of  any  part  of  the  engine  is  a  black 
mark  against  it. 

Find  out  how  much  attention,  011  an 
average,  the  engine  requires  per  day,  and 
just  what  the  nature  of  this  attention  is. 
If  the  engine  is  required  to  run  a  dynamo 
as  a  considerable  proportion  of  its  load, 
watch  the  lights  when  the  dynamo  is  run- 
ning. If  the  lights  show  no  perceptible 
winking,  when  the  light  is  observed  indi- 
rectly, the  engine  will  give  satisfactory  ser- 
vice for  electric  lighting  purposes.  A  good 
way  to  test  a  light  is  to  try  to  read  fine  print 
by  it.  If  the  light  throbs  to  too  great  an 
extent,  the  throbbing  will  be  quite  distinct 
and  the  eyes  will  quickly  tire.  If  the  pres- 
sure 011  the  lines  is  100  volts,  the  swing  of 
the  volt-meter  needle  should  not  exceed 
two  volts  when  swaying  back  and  forth. 
On  a  5o-volt  circuit  this  swing  should  not 
exceed  one  volt,  or  2%  of  the  pressure,  in 
any  case. 

If  the   engine    shakes   considerably  each 

205 


time  it  receives  an  impulse,  the  trouble  is 
due  to  an  insufficient  foundation,  but  if  this 
shaking  continues  when  the  engine  is  run- 
ning light,  i.  e.,  between  explosions,  the 
effect  is  due  to  improper  balancing. 

In  general,  select  an  engine  with  the 
fewest  number  of  parts,  and  with  the  parts 
so  arranged  that  they  maybe  easily  reached 
in  case  of  accident  or  when  repairs  of  any 
kind  are  necessary.  Don't  think,  because 
the  parts  are  encased,  that  the  engine  is  a 
simple  one,  for  the  opposite  may  be  the 
case.  An  engine  with  an  enclosed  mechan- 
ism may  be  a  very  good  one  for  all  that. 
The  point  that  the  writer  wishes  to  impress 
upon  the  reader  is,  that  it  should  not  be 
necessary  to  pull  the  entire  engine  to  pieces 
in  order  to  make  some  insignificant  repair 
or  adjustment. 


206 


LENGTH  OF  A  CYLINDRICAL  TANK  REQUIRED 
TO  HOLD  ONE  GALLON. 


Diam. 

Length 

Diam 

Length 

Ft. 

In. 

per  gal. 
in  feet. 

Ft.    In. 

per  gal. 
in  feet. 

1 

.1704 

11 

.00141 

1 

3 

.108 

11 

8 

.00131 

1 

6 

.0756 

11 

(') 

.00129 

1 

9 

.0556 

11 

9 

.00123 

2 

.043 

12 

.00118 

•> 

3 

.0337 

12 

3 

.00113 

2 

6 

.0273 

12 

C> 

.00109 

2 

9 

.0225 

12 

9 

.00105 

3 

.0189 

13 

.00101 

3 

3 

.0161 

13 

;; 

.000970 

3 

6 

.0139 

13 

6 

.000934 

3 

9 

.0121 

13 

9 

.000901 

4 

.0106 

14 

.000868 

4 

3 

.00943 

14 

3 

.000838 

4 

6 

.00841 

14 

6 

.000809 

4 

9 

.00755 

14 

9 

.000782 

5 

.00681 

1") 

.000756 

5 

3 

.00617 

15 

3 

.000732 

5 

6 

.00564 

15 

6 

.000708 

5 

9 

.00515 

15 

9 

.000686 

6 

.00472 

16 

.000665 

6 

3 

.00435 

l»i 

3 

.000645 

6 

.  6 

.00403 

l(i 

6 

.000(525 

i; 

9 

.00374 

16 

9 

.000606 

7 

.00347 

17 

.000589 

7 

3 

.00323 

17 

3 

.000572 

7 

6 

.00303 

17 

6 

.000556 

7 

9 

.00283 

17 

9 

.000540 

8 

.00266 

IS 

.000525 

s 

3 

.00250 

18 

.000511 

8 

6 

.00235 

18 

6 

.000497 

8* 

9 

.00222 

18 

9 

.000484 

9 

.00210 

19 

.000471 

9 

3 

.00199 

19 

3 

.000459 

9 

6 

.00189 

19 

6 

.0004  IS 

9 

9 

.00179 

19 

9 

.000437 

10 

.00170 

20 

.000426 

10 

3 

.00162 

20 

3 

.00041.". 

10 

6 

.00154 

20 

6 

.000405 

10 

9 

.00147 

20 

9 

.000395 

g 

w 

JH 
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3 


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208 


CIRCUMFERENCES    AND    AREAS 
OF    CIRCLES 

ADVANCING   BY   EIGHTHS. 


Diam. 

Circum. 

Area. 

Diam. 

Circum. 

Area. 

1-64 

.04909 

.00019 

1. 

3.1416 

.7854 

1-32 

.09818 

.00077 

1-16 

3.3379 

.XS66 

3-64 

.14726 

.00173 

y& 

3.5343 

.9940 

1-16 

.19635 

.00307 

3-16 

3.7306 

1.1075 

3-32 

.29452 

.00690 

M 

3.9270 

1.2272 

/^ 

.39270 

.01227 

5-16 

4.1233 

1.3530 

5-32 

.49087 

.01917 

'A/ 

4.3197 

1.4849 

3-16 

.58905 

.02761 

7-16 

4.5160 

1.6230 

7-32 

.68722 

.03758 

1^ 

4.7124 

1.7671 

9-16 

4.9087 

1.9175 

34 

.78540 

.04909 

5/s 

5.10'VL 

2.0739 

9-32 

.88357 

.06213 

11-16 

5.3014 

2.2365 

5-16 

.98175 

.07670 

% 

5.4978 

2.4053 

11-32 

1.0799 

.09281 

13-16 

5.6941 

2.5802 

% 

1.1781 

.11045 

% 

5.8905 

2.7612 

13-32 

1.2763 

.121)62 

15-16 

6.0868 

2.Dls:-5 

7-16 

1.3744 

.15033 

15-32 

1.4726 

.17257 

•>. 

6.2832 

3.1416 

1-16 

6.4795 

3.3410 

X 

1.5708 

.19635 

i  ' 

6.6759 

3.5466 

17-32 

1.66DO 

.22166 

3-16 

6.8722 

:  5.  75s:  5 

9-16 

1.7(571 

.24850 

I/ 

.0686 

3i97Cl 

19-32 

1.865:5 

.276S8 

5-16 

.264!) 

4.20CO 

% 

1.9635 

.30680 

:|/ 

.4613 

4.4301 

21-32 

2.0617 

.33824 

7-16 

.6576 

1.66C1 

11-16 

2.1598 

.37122 

1A 

7.8540 

4.90F7 

23-32 

2.2580 

.40574 

9-]  6 

S.050.0, 

5.1572 

5^ 

8.2467 

5.4110 

M 

2.3562 

.44179 

11-16 

8.44:50 

5.6727 

25-32 

2.4544 

.479:57 

/4 

8.6394 

5.9396 

13-16 

2.5525 

.51849 

13-16 

8.8357 

6.2T26 

27-32 

2.6507 

.55914 

i/ 

9.0:521 

().4918 

29-32 

2.7489 
2.8471 

.60132 
.64504 

15-16 

9.2284 

6.7771 

15-16 

2.9452 

.69029 

3. 

9.4248 

7.06S6 

31-32 

3.04:54 

.73708 

1-16 

9.6211 

7.3662 

209 


CIRCUMFERENCES    AND    AREAS  —  Continued. 


Diam. 

Circum 

Area. 

Diam. 

Circum. 

Area. 

'  3-16 

9.8175 
10.014 

7.6699 
7.9798 

13-16 

18.064 
18.261 

25.967 
26.535 

IX" 

10.210 

8.2958 

% 

18.457 

27.109 

5-16 

10.407 

8.6179 

15-16 

18.653 

27.688 

'.y 

10.603 

8.9462 

7-16 

10.799 

9.2806 

6. 

18.850 

28.274 

i/ 

10.996 

9.6211 

i/ 

19.242 

29.465 

9-16 

11.192 

9.9678 

~y 

19.635 

30.680 

5/ 

11.388 

10.321 

% 

20.028 

31.919 

11-16 

11.585 

10.680 

1/2 

20.420 

33.183 

13-16 

11.781 
11.977 

11.045 
11.416 

P 

20.813 
21.206 

34.472 
35.785 

12.174 

11.793 

% 

21.598 

37.122 

15-16 

12.370 

12.177 

7. 

21.991 

38.485 

4. 

12.566 

12.566 

}•'$ 

22.384 

39.871 

1-16 

12.763 

12.962 

% 

22.776 

41.282 

YB 

12.959 

13.364 

% 

23.169 

42.718 

3-fe 

13.155 

13.772 

Yi 

23.562 

44.179 

% 

13.352 

14.186 

/« 

23.955 

45.664 

5-16 

13  548 

14.607 

3^ 

24.347 

47.173 

'*% 

13.744 

15.033 

/& 

24.740 

48.707 

7^16 

13.941 

15.466 

14.137 

15.904 

8. 

25.133 

50.265 

9716 

14.334 

16.349 

i  '\ 

25.525 

51.849 

/^ 

14.530 

16.800 

/± 

25.918 

53.456 

11-16 

14.726 

17.257 

'% 

26.311 

55.088 

14.923 

17.728 

% 

26.704 

56.745 

13-16 

15.119 

18.190 

% 

27.096 

58.426 

/8 

15.315 

18.665 

d/ 

27.489 

60.132 

15-16 

15.512 

19.147 

% 

27.882 

61.862 

-1. 

15.708 

19.635 

9. 

28.274 

63.617 

"l-16 

15.904 

20.129 

% 

28.667 

65.397 

% 

16.101 

20.629 

% 

29.060 

67.201 

3-16 

16.297 

21.135 

II 

29.452 

69.029 

M 

16.493 

21.648 

29.845 

70.882 

5-16 

16.690 

22.166 

a 

30.238 

72.760 

% 

16.886 

22.691 

3^ 

30.631 

74.662 

7-16 

17.082 

23.221 

/8 

31.023 

76.589 

i/ 

17.279 

23.758 

9-16 

17.475 

24.301 

10. 

31.416 

78.540 

17.671 

24.850 

I/ 

31.809 

80.516 

11-16 

17.868 

25.406 

J;t 

32.201 

82.516 

CIRCUMFERENCES    AND    AREAS—  Continued. 


Diam. 

t 

Circum. 

Area. 

Diam. 

Circum. 

Area. 

10.% 

32.594 

84.541 

15.  K 

47.909 

182.65 

32.987 

86.590 

'&/ 

48.302 

185.66 

1 

33.379 
33.772 

88.664 
90.763 

1 

48.695 
49.087 

188.69 
191.75 

7/ 

34.165 

92.886 

'A/ 

49.480 

194.83 

H 

49.873 

197.93 

11. 

34.558 

95.033 

34.950 

97.205 

16. 

50.265 

201.06 

l/£ 

35.343 

99.402 

i/£ 

50.658 

204.22 

% 

35.736 

101.62 

*% 

51.051 

207.3U 

s 

36.128 

103.87 

'%> 

51.444 

210.60 

% 

36.521 

106.14 

i^ 

51.836 

213.82 

% 

36.914 

108.43 

0 

52.229 

217.08 

JX8 

37.306 

110.75 

3^ 

52.622 

220.35 

^8 

53.014 

223.65 

12. 

37.699 

113.10 

i^ 

38.092 

115.47 

17. 

53.407 

226.98 

/* 

38.485 

117.86 

% 

53.800 

230.33 

% 

38.877 

120.28 

i/ 

54.192 

233.71 

H 

39.270 

122.72 

% 

54.585 

237.10 

5/ 

39.663 

125.19 

/-/ 

54.978 

240.53 

'% 

40.055 

127.68 

zi 

55.371 

243.98 

% 

40.448 

130.19 

:{/i 

55.763 

247.45 

j£ 

56.156 

250.95 

13. 

40.841 

132.73 

% 

41.233 

135.30 

18. 

56.549 

254.47 

M 

41.626 

137.89 

i/ 

56.941 

258.02 

% 

42.019 

140.50 

/4 

57.334 

261.59 

i^ 

42.412 

143.14 

:Vs 

57.727 

265.18 

42.804 

145.80 

1? 

58.119 

268.80 

43.197 

148.49 

5/'' 

58.512 

272.45 

/b 

43.590 

151.20 

% 

58.905 

276.12 

% 

59.298 

279.81 

14. 

43.982 

153.94 

^8 

44.375 

156.70 

19. 

59.690 

283.53 

% 

44.768 

159.48 

i^ 

60.08;; 

287.27 

% 

45.160 

162.30 

/4 

60.476 

291.04 

I/ 

45.553 

165.13 

3/ 

60.868 

294.83 

0 

45.946 

167.99 

i| 

61.261 

298.  65 

K 

46.338 

170.87 

">s 

61.654 

302.49 

% 

46.731 

173.78 

:?  ( 

62.046 

306.35 

J? 

62.439 

310.24 

15. 

47.124 

176.71 

K 

47.517 

179.67 

20. 

62.832 

314.  1»» 

CIRCUMFKRKNCKS    AND    ARK  AS — Continued. 


IMam. 

Circum. 

Area. 

Diam. 

Circum. 

Area. 

CO.  % 

63  22-) 

31*  10 

2». 

78.540 

490.87 

X 

63.617 

322.06 

Ye 

78.933 

495.79 

% 

(U.010 

326.05 

y* 

79.325 

500.74 

Y* 

04.408 

330.06 

% 

79.718 

505.71 

7* 

61.795 

334.10 

Y 

80.111 

510.71 

i\ 

65.188 

338.16 

% 

80.503 

515.72 

65.581 

342.25 

/± 

80.896 

520.77 

/Q 

81.289 

525.84 

•>  | 

C5.973 

346.36 

A^ 

C.'i  :)66 

350.50 

26. 

81.681 

P30.93 

y± 

<;C).759 

354.66 

YB 

82.074 

536.05 

/« 

67.152 

358.84 

H 

82.467 

541.19 

i 

67.544 

(i7.9:57 

363.05 
367.28 

% 

82.860 
83.252 

546.35 
551.55 

:$ 

4 

68.330 

371.54 

5/8 

83.645 

556.76 

% 

68.722 

375.83 

% 

84.038 

562.00 

Y*. 

84.430 

567.27 

22. 

(>9.115 

380.13 

N 

69.508 

3S4.46 

27. 

84.823 

572.56 

g 

69.900 

388.82 

', 

85.216 

577.87 

P 

70.293 

393.20 

', 

85.608 

583.21 

70.686 

397.61 

::, 

86.001 

588.57 

% 

71.079 

402.04 

^2 

86.394 

593.96 

A 

71.471 

406.49 

H 

86.786 

599.37 

Ys 

71.864 

410.97 

% 

87.179 

604.,  il 

% 

87.572 

610:  ?7 

23. 

72.257 

415.48 

H 

72.649 

420.00 

28. 

87.965 

t>15.7  -> 

8 

73.042 

424.56 

% 

88.357 

621.26 

•% 

7:5.435 

429.13 

', 

88.750 

626.80 

s 

73.827 

4:5:  5.74 

% 

89.143 

632.36 

•'s 

74.220 

438.36 

'- 

89.535 

637.94 

% 

74.613 

443.01 

:>^ 

89.928 

C.43.55 

75.006 

447.69 

%! 

90.321 

649.18 

Ys 

t)0.7i:j 

654.84 

24. 

7.").39S 

452.:5!) 

X 

75.791 

457.11 

29. 

91.106 

660.52 

M 

76.184 

4C.I  si; 

i 

(J1.1!I(.> 

066.23 

% 

76.576 

4(16.64 

Y4 

91.892 

671.96 

8 

76.969 

471.44 

:;s 

92.284 

677.71 

•-•* 

77.362 

476.26 

', 

92.677 

683.49 

;, 

77.754 

4S1.11 

.-, 

93.070 

689.30 

% 

78.147 

485.98 

'% 

93.462 

695.13 

Y* 

93.855 

700.98 

CIRCUMFERENCES  AND  AREAS — Continued. 


Diam. 

Circum. 

Area. 

Diam. 

Circum. 

Area. 

30. 

94.248 

706.86 

35. 

109.956 

962.11 

% 

94.640 

712.76 

Ys 

110.348 

969.00 

V* 

95.033 

718.69 

% 

110.741 

975.91 

% 

95.426 

724.64 

'% 

111.134 

982.84 

H 

95.819 

730.62 

ft 

111.527 

989.80 

n 

96.211 

736.62 

II 

111.919 

99K.78 

% 

96.604 

742.64 

74: 

112.312 

1003.8 

jl 

96.997 

748.69 

% 

112.705 

1010.8 

81. 

97.389 

754.77 

36. 

113.097 

1017.9 

y. 

97.782 

760.87 

H 

113.490 

1025.0 

'4 

98.175 

766.99 

g 

113.883 

1032.1 

< 

98.567 

773.14 

\7 
78 

114.275 

1039.2 

s 

98.960 

779.31 

ft 

114.668 

1046.3 

jl 

99.353 

785.51 

|| 

115.061 

1053.5 

% 

99.746 

791.73 

^ 

115.454 

1060.7 

% 

100.138 

797.98 

% 

115.846 

1068.0 

32. 

100.531 

804.25 

37. 

116.239 

1075.2 

i/ 

100.924 

810.54 

•  ^ 

116.632 

1082.5 

'-1 

101.316 

816.86 

% 

117.024 

1089.8 

•\ 

101.709 

823.21 

% 

117.417 

1097.1 

H 

102.102 

829.58 

u 

117.810 

1104.5 

''s 

102.494 

835.97 

XH 

118.202 

1111.8 

i 

102.887 

842.39 

% 

118.596 

1119.2 

% 

103.280 

848.83 

% 

118.988 

1126.7 

38. 

103.673 

855.30 

38. 

119.381 

1134.1 

% 

104.065 

861.7!) 

T-/ 

119.773 

1141.0 

& 

104.458 

86S.31 

% 

120.166 

1149.1 

% 

104.851 

874.85 

% 

120.559 

1156.6 

X 

105.243 

881.41 

% 

120.9ol 

1164.2 

% 

105.636 

888.00 

'V 

121.344 

1171.7 

% 

106.02!) 

894.62 

% 

121.737 

1179.3 

7/8 

106.421 

901.26 

% 

122.129 

1186.9 

34. 

106.814 

907.92 

39. 

122.522 

1194.6 

H 

107.207 

914.61 

i/ 

122.915 

1  202.3 

i 

107.600 

921.32 

4 

123.308 

1210.0 

'  '  s 

107.992 

928.06 

% 

123.700 

1217.7 

K 

108.385 

934.82 

1 

124.093 

1225.4 

''s 

108.778 

941.61 

124.4X6 

1233.2 

:!4 

109.170 

948.42 

j2 

124.878 

1241.0 

7.s 

109.563 

955.25 

% 

125.271 

1248.8 

213 


CIRCUMFERENCES    AND    AREAS-  -Concluded. 


Diam. 

Circum. 

Area. 

Diam. 

Circum. 

Area. 

40. 

125.664 

1256.6 

45. 

141.372 

1590.4 

H 

126.056 

1264.5 

% 

141.764 

1599.3 

15 

126.449 

1272.4 

& 

142.157 

1608.2 

% 

126.842 

1280.3 

% 

142.550 

1617.0 

YL 

127.235 

1288.2 

A 

142.942 

1626.0 

% 

127.627 

1296.2 

78 

143.335 

1634.9 

% 

128.020 

1304.2 

% 

143.728 

1643.9 

/8 

128.413 

1312.2 

% 

144.121 

1652.9 

41. 

128.805 

1320.3 

46. 

144.513 

1661.9 

H 

129.198 

1328.3 

Ys 

144.906 

1670.9 

i| 

129.591 

1336.4 

% 

145.299 

1680.0 

/9> 

129.983 

1344.5 

•>8 

145.691 

1689.1 

J^Z 

130.376 

1352.7 

ft 

146.084 

1698.2 

ftZ 

130.769 

1360.8 

II 

146.477 

1707.4 

% 

131.161 

1369.0 

ft 

146.869 

1716.5 

% 

131.554 

1377.2 

'/8 

147.262 

1725.7 

42. 

131.947 

1385.4 

47. 

147.655 

1734.9 

•X 

132.340 

1893.7 

Ys 

148.048 

1744.2 

I/ 

132.732 

1402.0 

H 

148.440 

1753.5 

?» 

133.125 

1410.3 

'!s 

U8.X33 

176:2.7 

Iz 

1:58.51  <S 

1418.6 

% 

149.226 

1772.1 

/8 

133.910 

1427.0 

% 

149.618 

1781.4 

3% 

134.303 

1435.4 

% 

150.011 

1790.8 

% 

134.6% 

1443.8 

Ys 

150.404 

1800.1 

43. 

135.088 

1452.2 

48. 

150.796 

1809.6 

Yi 

135.481 

1460.7 

i,' 

151.189 

1819.0 

i/ 

135.874 

1469.1 

ft 

151.582 

182S.5 

3^ 

136.267 

1477.6 

% 

151.975 

1837.9 

1^ 

136.659 

1486.2 

% 

152.367 

1847.5 

§S 

137.052 

1194.7 

'\s 

152.760 

1857.0 

/4 

137.445 

1503.3 

% 

153.153 

1866.5 

% 

137.837 

1511.9 

H 

153.545 

1876.1 

44. 

138.230 

1520.5 

49. 

153.938 

1S85.7 

% 

138.623 

1529.2 

Y* 

154.331 

1X95.4 

is 

139.015 

1537.9 

i 

154.723 

1905.0 

'&/ 

139.408 

1546.6 

''s 

155.116 

1914.7 

\y 

139.  SOI 

1555.3 

ft 

155.509 

1924.4 

7» 

140.194 

1564.0 

Ys 

155.902 

193  J.  2 

74 

140.586 

1572.8 

% 

156.294 

194:5.9 

% 

140.979 

1581.6 

% 

156.687 

195:5.7 

2T4 


INDEX. 

PAGE 

Areas  of  circles,  table  of 209 

Automobile  engines 103 

Automobile  engines,  cooling  cylinders  of    ....  105 

Automobile  engines,  power  of 104 

"Backfiring" 37 

Balance-weights 167 

Balance-weights,  formulas  for 169 

Balance- weights,  location  of 169 

Barometer,  use  of  in  testing 182 

Batter,  in  foundations 175 

Battery,  care  of 30 

Battery  cells 38 

Beau  de  Rochas'  propositions 1 

Brake  arm,  determination  of  effect  of 200 

British  thermal  unit,  definition  of   .......  198 

Camshaft,  formula  for 177 

(Jam,  laying  out  a 78 

( -amshaf t,  position  of 7s 

Carbon,  deposits  of  in  cylinder «   37 

Carbureters 42,  44 

Carbureter,  defects  of 51 

Carbureter,  heating  a 50 

Care  of  an  engine 27 

Cells  for  battery 3s 

Circumferences  of  circles,  table  of 20!' 

Clearance,  percentage  of 19 1 

Clerk's  two-cycle  engine 5,  <> 

215 


PAGE 

Coal,  for  gas  producer '.   .    18 

Condenser,  use  of 03 

Connecting-rod 151 

Connecting-rod,  formulas  for 152 

Connecting-rod,  proportions  of .   .  150 

Con  tact  points,  destruction  of 6:5 

Cooling  tanks,  evaporation  in,  per  I.  H.  P 177 

Cooling  tanks,  size  of. 177 

Crank-pin,  formula  for -.   .   .  154 

Crankshafts 153 

Crankshafts,  formulas  for lf>;',,  154 

Crankshaft,  proportions  of 155 

Cylinder,  formulas  for  diameter  of  ....  123,  126, 127 

Cylinder,  proportions  of 129-134 

Cylinder  head 134 

Day  engine 6,  7,  70 

Diagrams 108 

Diagrams,  examples  of  actual.  fc .  116,  117 

Diagrams,  formulas  for 110,  111 

Diagram  from  gasoline  engine 120 

Diagram,  size  of 181 

Diesel  cycle,  comparison  with  others 15 

Diesel  cycle,  principles  of  operation  of  the     .   .   .  9-12 

Dimensions  of  a  gas  engine 121 

Efficiency,  thermal ' 199 

Electric  lights,  fluctuation  of  light  in 205 

Energy,  storage  of 101 

Engine,  shaking  of 20^ 

Exhaust  gases,  heat  carried  off  by 19s 

Explosion,  cause  of  weak , 36 

Explosions,  in  exhaust  passages 36 

Explosions,  premature 37 

Flame,  color  of 3.°> 

Flame,  trouble  with 38 

Flywheel,  computing  weight  of     ...      162 

Flywheel,  diameter  of 166 

Flywheel,  formula  for 163 

Flywheel,  proportions  of 165 

•  216 


PAGE 

Flywheels; 1M 

Foundation  bolts,  formula  for 176 

Foundations 171 

Foundations,  formula  for  weight  of 17:'! 

Foundations,  location  of 172 

Foundations,  materials  for 171 

Four-cycle,  comparison  with  others 18 

Four-cycle  engine,  principles  of  operation  .   .   .  2,  3,  5 

Frame 157 

Fuel,  power  derived  from 17 

Fuels 17-20 

Fuels,  table  of -'I 

Gases,  specific  heat  of 195 

Gases,  weight  of 19.~> 

Gasoline  engine,  power  of  a 19,  41 

Gasoline  engines 41 

Gasoline  engines,  attachments  for 42-48 

Gasoline  engine,  handling  a 49 

Gasoline  engine,  starting  a 49 

Gasoline  engine,  time  of  ignition  in 50 

Gasoline  fires,  how  to  extinguish 53 

Gasoline,  power  derived  from 19 

Gasoline,  precautions  in  handling 51 

Gasoline,  storage  of 52 

Gasoline  tanks,  construction  of 52 

Gasoline  tanks,  explosions  in 52 

Gas  producer 18 

Gas  valve,  adjustment  of 33 

Gears,  types  in  use 8:-! 

Governors 87 

Governors,  adjustment  and  care  of 33 

Governors,  examples  of 92-% 

Heat  absorbed  by  jacket  water 197 

Heat  absorbed  in  work 1.97 

Heat  carried  off  by  exhaust  gases 198 

Heat  values,  table  of 21 

Hornsby-Akroyd  engine -r>9 

Horsepower,  formulas  for 123,  200 

217 


PAGE 

Igniter,  adjustment  of :\t\ 

Igniter,  match 100 

Igniter,  setting  of 2s 

Igniters 54 

Ignition,  methods  of 54 

Ignition,  premature 37 

Ignition  tubes . 31 

Indicators isi 

Jacket  water,  flow  of .  .  177 

Jacket  water,  heat  absorbed  by     197 

Jacket  water,  management  of 32 

Jacket  water,  measurement  of isr> 

Jacket  water,  range  of  temperature  in 194 

Jets 44,  4<;,  59 

Jump-spark 67 

Kerosene  engines,  vaporizer  for 50 

Leaks,  remedies  for :'.9 

Make-and-break  igniter .   .  65,  67 

Manometer 1*2 

Marine  engine,  formula  for  size  of 17.S 

Mean  effective  pressure,  determination  of   ....  199 

Meter  for  testing 1*1 

Muffler,  formula  for 177 

Nash  engine «> 

Otto  cycle 2. 

Oil,  crank-case 29 

Oil,  cylinder 29 

Oil,  lubricating 28 

Pipe,  table  of  gas  and  water 20s 

Piston,  care  of - 3:i 

Piston-pin,  formula  for 151 

Piston,  proportions  of 1  IS 

Piston  rings 1 17 

Piston-rods  in  gas  engines 1 1<> 

Piston,  trunk 1 17 

Plauimeter,  use  of 19'.' 

Pounding,  cause  of 39 

Power,  loss  of :>9 

2lS 


PAGE 

Premature  explosions 37 

Pressure,  coefficients  for  reduction  of 197 

Prony  brake isi 

Propellers,  formula  for 178 

Pyrometer 182 

Katio  of  gas  to  air 194 

Resistance,  non-inductive 63 

Scale,  testing  a  platform        181 

Selection 20:1 

Slowing  down,  cause  of ;;6 

Smoke,  cause  of 39 

Soot,  in  exhaust  passages 29 

Spark,  cause  of  weak 38 

Speed,  formulas  for 12.~> 

Speed  variation Kid 

Speed  variation,  allowable 16.5 

Springs,  adjustment  of 30,  3<; 

Starting,  rules  for 22 

Starters 97 

Stopping,  rules  for 25 

Suction  valve 71 

Table  of  areas  and  circumferences  of  circles  .   .  .  209 

Table  of  capacity  of  cylindrical  vessels 207 

Table  of  gas  and  water  pipe 208 

Table  of  heat  values 21 

Tanks,  table  of  capacity  of  cylindrical 207 

Temperature,  formula  for  reduction  to  standard  .  196 

Temperature,  reduction  to  standard 196 

Test,  apparatus  for 181,  183 

Test,  customary  determinations  in  a  factory  .  .   .  202 

Test,  log  for 188 

Test,  measurements  for 190 

Test,  method  of  conducting  a 187 

Test,  number  of  runs  in  a 189 

Test,  objects  off , ISO 

Test,  report  of  ! 192,19:; 

Testing 180 

Thermal  efficiency 199 

219 


Thermometers 1s- 

Timing  valve 5s 

Tubes,  material  for  ignition 31 

Tubes,  proper  temperature  for  ignition 31 

Troubles,  gas-engine 35 

Two-cycle,  comparison  with  others 14 

Two-cycle  engine,  principles  of  operation  ...  7,    i> 

Valves,  arrangement  of 141-145 

Valve  boxes,  examples  of 141-145 

Valves,  leaks  in :!0,  :«' 

.  Valve  mechanisms 73 

Valves,  proportions  of 139,  HO 

Valves,  size  of 136-139 

Valve-stems,  care  of 34,  40 

Vaporizers 4-J,  4f> 

Water,  flow  of  in  jacket 177 

Water,  formula  for  weight  of ]!>! 

Water-jacket,  deposit  in 29 

Water,  measurement  of  jacket 1*5 

Water  pipe,  table  of 20s 

Weak  spark,  cause  of :->* 

Wipe  break 63,07 

Work,  heat  absorbed  by 197 


220 


1 

**,  The... 

"WATKINS" 

GAS  AND  GASO- 

LINE ENGINES* 

± 

*jf 

Only  Engine  using 

cMagneto 
Generator 

No  Hot  Tubes. 

No  ^Batteries. 

Descriptive  Catalogue  on  application. 

F.  ML  WATKINS, 

309  West  Fourth  Street, 

CINCINNATI,  OHIO. 

GASOLINE 
ENGINES.. 


STATIONARY,  CARRIAGE   AND 
LAUNCH    ENGINES. 

VL  to  4  H    P       *    Flange-Cooled  and 

r    Water-Jacketed  Cylinders. 


CARBURETORS, 

GASOLINE   MIXING  VALVES, 

PROPELLER  WHEELS  and  SHAFTS. 

Also  complete  sets  of  Castings  of  Gasoline 
Engines,  with  Forgings,  Screws  and  Working 
Drawings,  either  in  rough  or  partly  ma- 
ehined,  as  required. 

LOWELL  MODEL  CO., 

P.  O.  BOX  292,     -    -     LOWELL,  MASS. 


GAS 

If  you  have  a  Gas  Engine,  send 
for  a  sample  of     QJXON'S 

No.  635  GRAPHITE. 

It  will  lubricate  your  Gas  Engine  Cylinder  better 
than  oil.    It  is  not  affected  by  heat. 

JOSEPH  DIXON  CRUCIBLE  CO. 

JERSEY   CITY,  N.J. 


PATENTS 


secured   in  the   United 
States  and  foreign  coun- 

mmmmmmmmmmi^^fmmmi^i^t      trieS.       Investigations   aS 

to  novelty  and  validity.  Litigation  conducted 
in  the  Courts  and  Patent  Office.  Trade  Marks 
registered.  Members  of  the  bar  of  the  United 
States  Supreme  Court  and  various  Circuit  Courts. 

BALDWIN,  DAVIDSON  &  WIGHT, 


25  Grant  Place, 

WASHINGTON,  D.  C. 


141  Broadway, 

NEW  YORK. 


THERE/A  LITTLE  BOOK-TELL/ WHV 


" WHICH  WAY"  POCKET  LEVEL.. 

TELLS  in  an  instant  "WHICH 
WAY"  your  work  is  out.  See? 
It  is  the  size  of  a  silver  dollar  and 
three  -  eighths  thick.  Nicely 
nickeled  and  polished.  To  in- 
troduce it,  will  mail  one  for  70c. 
in  stamps  or  three  for  $2.00.  Caliper  catalog  free. 

E.  G.  SMITH,  Columbia,  Pa.,  U.  S.  A. 


Attractive  Catalogues 
^  Carefully  Edited^ 


"WTE  offer  a  service  that  is 
W  unsurpassed,  including 
p  r  i  n  t  i  n  g  ,  half  tones, 
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chanical engineer  of  demon- 
strated ability,  who  is  a  for- 
cible writer  on  mechanical 
subjects,  and  of  wide  experi- 
ence, is  specially  engaged  to 
do  the  editing*  We  make  a 
specialty  of  catalogues  that 
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for  estimates*  We  know  that 
we  can  please  you*  Address 

The    Ohio    Printing     Co*, 

330  W.  9th  Street,    -    -   Cincinnati,  Ohio. 


The  Mietz  &  Weiss 

KEROSENE  ENGINE 


[Patented.] 


COMMON     KEROSENE     ITS    FUEL. 

%  CENT  PER  HORSEPOWER  PER  HOUR. 
IGNITES   BY    COMPRESSION. 

MOST  ECONOMICAL  AND   SAFEST 
POWER  KNOWN 

128-132  MOTT  ST., 
NEW  YORK. 

MARKT    &,    COMPANY,  LTD., 

EUROPEAN    AGENTS. 

LONDON.  HAMBURG.  PARIS. 


WORKING  DRAWINGS  FOR  SALE, 

0a$  and  Gasoline  Engines 

Horizontal,  Stationary,   -    -         -    -    12  sizes. 
Vertical  and  Marine,  ."-."-      4  sizes. 

Steam  Engines. 

Corliss,  simple  and  compound,    -  -    12  sizes. 

Center  Crank, 4  sizes. 

Ant,  High-Speed,    -                 -    -  -    10  sizes. 

QIDDINQS  &  STEVENS, 

Mechanical  Engineers,  ROCKPORD,  ILL. 

There  are  10,000  Laundries  in 
the  United  States  and  Canada. 

THE    STARCHROOM 

LAUNDRY  JOURNAL 

Write  for  rates.  Covers  the  Entire  Trade. 

The  Starch  room  Publishing  Co., 

Cincinnati,  Ohio. 


Cbe  6as  Engine 

magazine. 

Stationary, 

marine, 

flutomobik. 

Devoted  10  the  interests  of  an  up-to-date  power. 
illustrated. 


edited  by  G.  01.  Roberts, 


the  6a$  engine  contains  tbe  latest  news 

relating  to  tbe  das  engine  and 

tbe  automobile. 


Special  Teatum, 

'^e  e(^^0"a^s  8lve  a  monthly 
review  of  the  gas  engine  situation 
in  general. 


Special  Articles,      sPedal  articles  app«ar 

each    month    which     deal 
with  the  gas  engine  and  kindred  subjects. 


foreign  Correspondence,      We  hav*  just 

made  arrange- 
ments with  a  well-known  expert  in  Europe  to  keep 
our  readers  informed  on  the  latest  developments 
across  the  Atlantic. 


TtettlS.  ™e  industrial  columns 

contain     information     re- 


garding new  enterprises. 


Automobile  news,      This  column  gives  se 

lected     items    of    news, 
relating  to  automobiles. 


The  inquiry  column  is  at  the 
service  of  our  subscribers,  and  is 
one  of  the  most  valuable  features  of  the  magazine. 
All  questions  are  answered  carefully  and  in  full. 


The  gas  engine  is,  without  a  shadow  of  doubt,  the 
power  par  excellence  of  the  Twentieth  Century. 
Engineers  and  mechanics,  the  world  over,  are  studying 
its  developments  with  interest.  The  Gas  Engine  is 
the  only  publication  in  the  English  language  devoted 
to  this  subject.  It  will  keep  you  informed,  and  at 
the  insignificant  outlay  of  $1.00  each  year  for  the 
twelve  issues.  Send  for  a  sample  copy  to  THE 
GAS  ENGINE  PUBLISHING  CO.,  Goodall  Build- 
ing, Cincinnati,  Ohio. 


«i"J< 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 


AN  INITIAL  PINE  OP  25  CENTS 

WILL  dE  ASSESSED  FOR  FAILURE  TO  RETURN 
THIS  BOOK  ON  THE  DATE  DUE.  THE  PENALTY 
WILL  INCREASE  TO  SO  CENTS  ON  THE  FOURTH 
DAY  AND  TO  $!.OO  ON  THE  SEVENTH  DAY 
OVERDUE. 


SEP  27  1939 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


